Transparent invisible conductive grid

ABSTRACT

The present invention relates to an antistatic article comprising a substrate or support having thereon at least one antistatic layer, wherein the antistatic layer comprises a conductive material having areas of patterned coverage. The present invention also relates to a display comprising a substrate having an electrically modulated imaging layer thereon, at least one electrically conductive layer, and at least one transparent antistatic layer, wherein said antistatic layer comprises a conductive material having areas of patterned coverage.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a Continuation-In-Part of U.S. patent application Ser. No.10/668,386 filed Sep. 23, 2003 by Aylward et al. entitled “TransparentInvisible Conductive Grid”.

FIELD OF THE INVENTION

The present invention relates to an antistatic layer having areas ofpatterned coverage applied to a support or a substrate.

BACKGROUND OF THE INVENTION

The problem of controlling static charge during plastic webmanufacturing and transport is well known. Generation and uncontrolleddischarge of electrostatic charge can cause a number of serious problemsincluding safety hazards. In the field of imaging, particularlyphotography, the accumulation of charge on film or paper surfaces leadsto the attraction of dirt, which can produce physical defects. Thedischarge of accumulated charge during or after the application of thesensitized emulsion layer(s) can produce irregular fog patterns or“static marks” in the emulsion. The static problems have been aggravatedby increase in the sensitivity of new emulsions, increase in coatingmachine speeds, and increase in post-coating drying efficiency. Thecharge generated during the coating process may accumulate duringwinding and unwinding operations, during transport through the coatingmachines and during finishing operations such as slitting and spooling.

It is generally known that electrostatic charge can be dissipatedeffectively by incorporating one or more electrically-conductive“antistatic” layers into the support structure. Typical location of anantistatic layer is an external surface, which comes in contact withvarious transport rollers. For imaging elements, the antistatic layer isusually placed on the side of the support opposite to the imaging layer.The imaging element may also have a dual system for control of static inwhich the resin-coated paper contains both ionically conductive saltsand water as well as a conductor on the outside of the backside resinlayer.

A wide variety of electrically-conductive materials can be incorporatedinto antistatic layers to produce a wide range of conductivities. Thesecan be divided into two broad groups: (i) ionic conductors and (ii)electronic conductors. In ionic conductors charge is transferred by thebulk diffusion of charged species through an electrolyte. Here theresistivity of the antistatic layer is dependent on temperature andhumidity. Antistatic layers containing simple inorganic salts, alkalimetal salts of surfactants, ionic conductive polymers, polymericelectrolytes containing alkali metal salts, and colloidal metal oxidesols (stabilized by metal salts), described previously in patentliterature, fall in this category. However, many of the inorganic salts,polymeric electrolytes, and low molecular weight surfactants used arewater-soluble and are leached out of the antistatic layers duringprocessing, resulting in a loss of antistatic function. The conductivityof antistatic layers employing an electronic conductor depends onelectronic mobility rather than ionic mobility and is independent ofhumidity. Antistatic layers which contain conjugated polymers,semiconductive metal halide salts, and semiconductive metal oxideparticles, have been described previously. However, these antistaticlayers typically contain a high volume percentage of electronicallyconducting materials, which are often expensive and impart unfavorablephysical characteristics, such as color, increased brittleness and pooradhesion, to the antistatic layer.

A vast majority of the prior art involves coatings of antistatic layersfrom aqueous or organic solvent based coating compositions. Forphotographic paper, typically antistatic layers based on ionicconductors, are coated out of aqueous and/or organic solvent basedformulations, which necessitate an effective elimination of the solvent.Under fast drying conditions, as dictated by efficiency, formation ofsuch layers may pose some problems. An improper drying will invariablycause coating defects and inadequate adhesion and/or cohesion of theantistatic layer, generating waste or inferior performance. Pooradhesion or cohesion of the antistatic layer can lead to unacceptabledusting and track-off. A discontinuous antistatic layer, resulting fromdusting, flaking, or other causes, may exhibit poor conductivity, andmay not provide necessary static protection. It can also allow leachingof calcium stearate from the paper support into the processing tankscausing build-up of stearate sludge. Flakes of the antistatic backing inthe processing solution can form soft tar-like species, which, even inextremely small amounts, can re-deposit as smudges on drier rollerseventually transferring to image areas of the photographic paper,creating unacceptable defects.

Moreover, majority of conductive materials used as antistats on currentphotographic paper products lose their electrical conductivity afterphotographic processing due to their ionic nature. This can cause printsticking after drying in the photoprocessor, and/or in a stack. Otherimaging elements that are on resin coated paper bases have a dual systemfor control of static in which the paper contains both ionicallyconductive salts and water as well as a conductor on the outside of thebackside resin layer.

In U.S. Pat. Nos. 6,197,486 and 6,207,361, antistatic layers have beendisclosed which can be formed through the (co)-extrusion method thuseliminating the need to coat the support in a separate step andrendering the manufacturing process less costly.

With the development of all plastic web media, such as, for example,foam-core polymer sheets, the conductivity requirements of the plasticweb media are typically increased because there is no paper base thatcontains water and salt to provide conductivity. The web media mayrequire the addition of an electronically conducting material such astin oxide, polythiophene and others. Some of these materials have colorassociated with them at various coverages. These materials are also veryexpensive when compared to more conventional conductive compounds.

PROBLEM TO BE SOLVED

There remains a need for conductive materials for use on a number ofsubstrates and supports, which are simpler to manufacture, utilize lessraw materials and are lower in cost.

SUMMARY OF THE INVENTION

The present invention relates to an antistatic article comprising asupport, referred to herein also as a substrate, having thereon at leastone antistatic layer, wherein the antistatic layer comprises aconductive material having areas of patterned coverage. The presentinvention also relates to a display comprising a substrate having anelectrically modulated imaging layer thereon, at least one electricallyconductive layer, and at least one transparent antistatic layer, whereinsaid antistatic layer comprises a conductive material having areas ofpatterned coverage.

ADVANTAGEOUS EFFECT OF THE INVENTION

The present invention includes several advantages, not all of which areincorporated in a single embodiment. Coating the antistatic layer in apatterned format provides a network of conductive pathways at asignificantly reduced coverage (up to 80–90% reduction). The pattern maybe a simple grid pattern or any other interconnected labyrinthinepattern. The significant reduction in coverage of the antistatic layerof the invention leads directly to savings in material costs. Thepresent invention can also provide additional benefits in frictioncontrol and improved transport through image processing equipment. Theoverall reduced coverage of the conductive material minimizes thepotential for dusting during manufacturing, transport, finishing orphotofinishing. The antistatic layer also reduces the potential forcontamination of the processing chemicals and associated sensitometricinteractions due to any conductive material coming off duringprocessing.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to an article, for example, an imagingelement, comprising a substrate or support having at least oneantistatic layer, wherein said antistatic layer comprises a conductivematerial having areas of patterned coverage. In particular, the presentinvention relates to a display comprising a substrate having anelectrically modulated imaging layer thereon, at least one electricallyconductive layer, and at least one transparent antistatic layer, whereinsaid antistatic layer comprises a conductive material having areas ofpatterned coverage. The antistatic layer may optionally comprise apolymeric binder or carrier for improved physical properties. Thisinvention provides a pattern, preferably a transparent and/or invisibleelectrostatic pattern, such as a grid, on a substrate or support, as ameans to reduce the coverage of conductive materials required forvarious coatable supports, for examples, imaging elements. Embodimentsof this invention may include coatings on a substrate or supportcomprising a background layer containing a conductive material withintegral design, such as a logo, that comprises a non-continuous outlinewith an optical density different than that optical density of thebackground layer, and an interior region of the logo or design that isalso conductive. The interior of the logo may be the same or differentcoverage that may provide some additional contrast between thebackground and the logo. The outline area may have no coverage andtherefore only show the background of the substrate or it may be ahigher coverage of the conductive material. Other embodiments mayinclude a substrate comprising a background layer containing conductivematerial with an integral design, for example, a logo, that comprises anoptical density different than background layer and an interior regionof the logo that may be conductive or non-conductive which may beprinted at a different coverage than the background layer in order toprovide contrast between the background and the logo or design. The logoarea may have no coverage and therefore only show the background of thesubstrate or it may be a higher or lower coverage than that of thebackground antistatic material. In another embodiment, a substrate maycomprise a conductive grid pattern and an integral logo. The pattern mayprovide a means of conducting a charge through the logo's interior. Inanother embodiment, the substrate may have a conductive background layercoated with a conductive grid pattern of different coverage. In oneembodiment, the substrate may have a background layer with a lowercoverage of conductive material than a grid pattern coated thereon. Inthis case the background area can still transport electrical charge tothe primary conductor as represented by grid pattern. The presentinvention may provide advantages when utilized in other applications aswell, such as labeling materials, packaging materials, includingelectronic packaging that requires an antistatic layer to prevent staticdischarge and prevent damage to an electronic device.

The terms as used herein, “top”, “upper”, “emulsion side”, and “face”mean the side or toward the side of the imaging member bearing theimaging layers. The terms “bottom”, “lower side”, and “back” mean theside or toward the side of the imaging member opposite from the sidebearing the imaging layers or image. The “image side” of the support isthe side on which imaging layers would be applied. The “non-image side”of the support is the side of support opposite the imaging layers.

The antistatic layer of the present invention comprises an electricallyconductive material and may include ionic conductors and electronicconductors. The conductive material, when utilized in an antistaticlayer, preferably produces an antistatic layer having a resistivity ofless than 10¹³ ohm/sq., most preferably, a resistivity less than 3×10¹²ohm/sq. In a preferred embodiment, the conductivity ranges between 10¹³and 10⁷ ohms/sq.

Electronic conductors, such as conjugated conducting polymers,conducting carbon particles, crystalline semiconductor particles,amorphous semiconductive fibrils, and continuous conductive metal orsemiconducting thin films may be used in this invention to affordhumidity independent, process-surviving antistatic protection. Of thevarious types of electronic conductors, electronically conductivemetal-containing particles, such as semiconducting metal oxides, andelectronically conductive polymers, such as, substituted orunsubstituted polythiophenes, substituted or unsubstituted polypyrroles,and substituted or unsubstituted polyanilines are particularly effectivefor the present invention.

Conductive metal-containing particles, which may be used in the presentinvention include conductive crystalline inorganic oxides, conductivemetal antimonates, and conductive inorganic non-oxides. Crystallineinorganic oxides may be chosen from zinc oxide, titania, tin oxide,alumina, indium oxide, silica, magnesia, barium oxide, molybdenum oxide,tungsten oxide, and vanadium oxide or composite oxides thereof, asdescribed in, for example, U.S. Pat. Nos. 4,275,103, 4,394,441,4,416,963, 4,418,141, 4,431,764, 4,495,276, 4,571,361, 4,999,276 and5,122,445.

The conductive crystalline inorganic oxides may contain a “dopant” inthe range from 0.01 to 30 mole percent. Preferred dopants may includealuminum or indium for zinc oxide, niobium or tantalum for titania, andantimony, niobium or halogens for tin oxide. Alternatively, theconductivity can be enhanced by formation of oxygen defects by methodswell known in the art. The use of antimony-doped tin oxide particles,such as those having an X-ray crystallite size less than 100 Å and anaverage equivalent spherical diameter less than 15 nm but no less thanthe X-ray crystallite size as taught in U.S. Pat. No. 5,484,694, isspecifically contemplated.

Particularly useful electronically conductive metal-containingparticles, which may be used in the antistatic layer, include aciculardoped metal oxides, acicular metal oxide particles, acicular metaloxides containing oxygen deficiencies. In this category, acicular dopedtin oxide particles, particularly acicular antimony-doped tin oxideparticles, acicular niobium-doped titanium dioxide particles, arepreferred because of their availability. The aforesaid acicularconductive particles preferably have a cross-sectional diameter lessthan or equal to 0.02 μm and an aspect ratio greater than or equal to5:1. Some of these acicular conductive particles, useful for the presentinvention, are described in U.S. Pat. Nos. 5,719,016, 5,731,119,5,939,243 and references therein.

The volume fraction of the acicular electronically conductive metaloxide particles in the dried antistatic layer of the invention may varyfrom 1 to 70% and preferably from 5 to 50% for optimum physicalproperties. For non-acicular electronically conductive metal oxideparticles, the volume fraction may vary from 15 to 90%, and preferablyfrom 20 to 80% for optimum properties.

The invention is also applicable where the conductive agent comprises aconductive “amorphous” gel such as vanadium oxide gel comprised ofvanadium oxide ribbons or fibers. Such vanadium oxide gels may beprepared by any variety of methods, including but not specificallylimited to melt quenching as described in U.S. Pat. No. 4,203,769, ionexchange as described in DE 4,125,758, or hydrolysis of a vanadiumoxoalkoxide as claimed in WO 93/24584. The vanadium oxide gel ispreferably doped with silver to enhance conductivity. Other methods ofpreparing vanadium oxide gels, which are well known in the literature,include reaction of vanadium or vanadium pentoxide with hydrogenperoxide and hydrolysis of VO₂ OAc or vanadium oxychloride.

Conductive metal antimonates suitable for use in accordance with theinvention include those as disclosed in, U.S. Pat. Nos. 5,368,995 and5,457,013, for example. Preferred conductive metal antimonates have arutile or rutile-related crystallographic structures and may berepresented as M⁺² Sb⁺⁵ ₂ O₆ (where M⁺²=Zn⁺², Ni⁺², Mg⁺², Fe⁺², Cu⁺²,Mn⁺², Co⁺²) or M⁺³ Sb⁺⁵ O₄ (where M^(+3=In) ⁺³, Al⁺³, Sc⁺³, Cr⁺³, Fe⁺³).Several colloidal conductive metal antimonate dispersions arecommercially available from Nissan Chemical Company in the form ofaqueous or organic dispersions. Alternatively, U.S. Pat. Nos. 4,169,104and 4,110,247 teach a method for preparing M⁺² Sb⁺⁵ ₂ O₆ by treating anaqueous solution of potassium antimonate with an aqueous solution of anappropriate metal salt (for example, chloride, nitrate, sulfate) to forma gelatinous precipitate of the corresponding insoluble hydrate whichmay be converted to a conductive metal antimonate by suitable treatment.If used, the volume fraction of the conductive metal antimonates in thedried antistatic layer can vary from 15 to 90%. But it is preferred tobe from 20 to 80% for optimum physical properties.

Conductive inorganic non-oxides suitable for use as conductive particlesin the present invention include metal nitrides, metal borides and metalsilicides, which may be acicular or non-acicular in shape. Examples ofthese inorganic non-oxides include titanium nitride, titanium boride,titanium carbide, niobium boride, tungsten carbide, lanthanum boride,zirconium boride, or molybdenum boride. Examples of conductive carbonparticles, include carbon black and carbon fibrils or nanotubes withsingle walled or multi-walled morphology. Example of such suitableconductive carbon particles can be found in U.S. Pat. No. 5,576,162 andreferences therein.

Suitable electrically conductive polymers that are preferred forincorporation in the antistatic layer of the invention are specificallyelectronically conducting polymers, such as those illustrated in U.S.Pat. Nos. 6,025,119, 6,060,229, 6,077,655, 6,096,491, 6,124,083,6,162,596, 6,187,522, and 6,190,846. These electronically conductivepolymers include substituted or unsubstituted aniline-containingpolymers (as disclosed in U.S. Pat. Nos. 5,716,550, 5,093,439 and4,070,189), substituted or unsubstituted thiophene-containing polymers(as disclosed in U.S. Pat. Nos. 5,300,575, 5,312,681, 5,354,613,5,370,981, 5,372,924, 5,391,472, 5,403,467, 5,443,944, 5,575,898,4,987,042 and 4,731,408), substituted or unsubstitutedpyrrole-containing polymers (as disclosed in U.S. Pat. Nos. 5,665,498and 5,674,654), and poly(isothianaphthene) or derivatives thereof. Theseconducting polymers may be soluble or dispersible in organic solvents orwater or mixtures thereof. Preferred conducting polymers for the presentinvention include polypyrrole styrene sulfonate (referred to aspolypyrrole/poly (styrene sulfonic acid) in U.S. Pat. No. 5,674,654),3,4-dialkoxy substituted polypyrrole styrene sulfonate, and 3,4-dialkoxysubstituted polythiophene styrene sulfonate because of their color. Themost preferred substituted electronically conductive polymers includepoly(3,4-ethylene dioxythiophene styrene sulfonate), such as Baytron® Psupplied by Bayer Corporation, for its apparent availability inrelatively large quantity. The weight % of the conductive polymer in thedried antistatic layer of the invention may vary from 1 to 99% butpreferably varies from 2 to 30% for optimum physical properties.

Humidity dependent, ionic conductors are traditionally morecost-effective than electronic conductors and find widespread use inreflective imaging media such as paper. Any such ionic conductor can beincorporated in the antistatic layer of the invention. The ionicconductors can comprise inorganic and/or organic salt. Alkali metalsalts, particularly those of polyacids, may be effective. The alkalimetal can comprise lithium, sodium or potassium and the polyacid cancomprise polyacrylic or polymethacrylic acid, maleic acid, itaconicacid, crotonic acid, polysulfonic acid or mixed polymers of thesecompounds, as well as cellulose derivatives. The alkali salts ofpolystyrene sulfonic acid, napthalene sulfonic acid or an alkalicellulose sulfate are preferred for their performance.

The combination of polymerized alkylene oxides and alkali metal salts,described in U.S. Pat. Nos. 4,542,095 and 5,683,862 incorporated hereinby reference, is also a preferred choice. Specifically, a combination ofa polyethylene ether glycol and lithium nitrate is a desirable choicebecause of its performance and cost. Also, preferred are inorganicparticles such as electrically conductive synthetic or natural smectiteclay. Of particular preference for application in the present inventionare those ionic conductors, such as an alkali metal salt incombinationwith a polymeric latex binder and a non-ionic surface active compoundcontaining, as described in U.S. Pat. No. 5,683,862, a smectite clay incombination with an interpolymer of vinylidene halide, as described inU.S. Pat. No. 5,869,227, a smectite clay, and a polymeric binder whereinthe polymeric binder can sufficiently intercalate inside or exfoliatethe smectite clay, as described in U.S. Pat. No. 5,891,611, a smectiteclay, a first polymeric binder which sufficiently intercalates inside orexfoliates the smectite clay and a second polymeric binder which doesnot sufficiently intercalate inside or exfoliate the smectite clay, asdescribed in U.S. Pat. No. 5,981,126, a combination of an alkali metalsalt and a polymerized alkylene oxide, a positively charged colloidaloxide sol and a film forming binder which is an interpolymer of aprimary amine addition salt with a peel strength of 200 g or above on apolyolefin surface, as described in U.S. Pat. No. 6,077,656, and acombination of an alkali metal salt and a polymerized alkylene oxide,colloidal silica, preferably aluminum modified colloidal silica, and apolymeric film-forming binder with a peel strength of 200 g or above ona polypropylene surface, as described in U.S. Pat. No. 6,171,769, andreferences therein.

Another suitable group of polymeric conductive materials, which are wellknown in the art for their excellent melt-processabilty while retainingtheir antistatic property and overall physical performance, may includepolyether based polymeric antistatic compounds containingpolyalkoxylated compounds. These materials can include various polymericsubstances containing polyether blocks such as polyethylene oxides,polypropylene oxides, polybutylene oxides, polytetramethylene oxides,polyoxyalkylene glycols such as polyoxyethylene glycol, polyoxypropyleneglycol, polyoxytetramethylene glycol, the reaction products ofpolyalkoxylates with fatty acids, the reaction products ofpolyalkoxylates with fatty alcohols, the reaction products ofpolyalkoxylates with fatty acid esters of polyhydroxyl alcohols (forinstance polyalkoxylate reaction products of fatty acids, of fattyglycols, of fatty sorbitols, of fatty sorbitans, and of fatty alcohols),or, interpolymers and/or mixtures thereof. The polyether chains in thesuitable polyalkoxylated compounds are of the formula (—OC_(x)H_(2x)—)_(n) wherein x is from 2 to 8, wherein the alkyl group isstraight or branched, and wherein n is from 2 to 1000. It is believedthat ionic conduction along the polyether chains makes these polymersinherently dissipative, yielding surface resistivities in the range10⁸–10¹³ ohm/square.

For the purpose of this invention, any polyalkoxylated compoundscontaining oligomer, homopolymer, interpolymer and/or mixtures thereofcan suitably be used in this invention. However, preferred examples ofsuch polyether polymeric conductive materials are: those comprisingpolyamide blocks and polyether block(s), for example, as disclosed inU.S. Pat. Nos. 4,331,786, 4,115,475, 4,195,015, 4,839,441, 4,864,014,4,230,838, 4,332,920, 6,197,486, 6,207,361, 6,436,619, 6,465,140 and6,566,033 and product literature for Pebax supplied by Elf Atochem orIrgastat currently supplied by Ciba Specialty Chemicals,polyetheresteramides, for example, as disclosed in U.S. Pat. Nos.5,604,284; 5,652,326; 5,886,098, and thermoplastic polyurethanescontaining a polyalkylene glycol moiety, for example, as disclosed inU.S. Pat. Nos. 5,159,053; 5,863,466, with the content of all of theaforementioned literature incorporated herein by reference. Mostpreferred polyether polymeric conductive compounds used as antistats arethose comprising polyamide blocks and polyether block(s).

Surfactants capable of static dissipation are also suitable forapplication in the present invention. Such surfactants are usuallyhighly polar compounds and can be anionic, cationic or non-ionic ormixtures thereof, as described in U.S. Pat. No. 6,136,396 hereinincorporated by reference. Examples of anionic surfactants includecompounds such as those comprising alkyl sulfates, alkyl sulfonates andalkyl phosphates having alkyl chains of 4 or more carbon atoms inlength. Examples of cationic surfactants include compounds such as oniumsalts, particularly quaternary ammonium or phosphonium salts, havingalkyl chains of 4 or more carbon atoms in length. Examples of non-ionicsurfactants include compounds such as polyvinyl alcohol,polyvinylpyrrolidone and polyethers, as well as amines, acids and fattyacid esters having alkyl groups of 4 or more carbon atoms in length.Surfactants can also be effectively used for charge balancing, as perthe present invention. In this case, suitable surfactants are chosen tocounter balance the tribocharge generated on the surface.

The conductive particles that can be incorporated in the antistaticlayer are not specifically limited in particle size or shape. Theparticle shape may range from roughly spherical or equiaxed particles tohigh aspect ratio particles such as fibers, whiskers, tubes, plateletsor ribbons. Additionally, the conductive materials described above maybe coated on a variety of other particles, also not particularly limitedin shape or composition. For example the conductive inorganic materialmay be coated on non-conductive silica, alumina, titania and micaparticles, whiskers or fibers.

In one embodiment useful in this invention, the patterns of conductivematerial are machine detectable and not visible to the human eye undernatural or artificial daylight illuminance. The pattern of machinedetectable conductive material may respond to actinic radiation below400 nanometers or above 700 nanometers. Such machine detectableconductive materials not visible to the human eye under daylightilluminance may be applied to the substrate or support. In anotherembodiment, the patterns of the conductive material may be visible tothe human eye under natural or artificial daylight illuminance. In anembodiment of this invention there may be at least two regions of theconductive material. There may be a background region for conductingcharge and a logo or indicia region that has sufficient density or colordifference that the background region. In such an embodiment it is thecontrast difference that make the logo visible. The logo may be furtherpatterned with a grid of connecting lines or patterns so as toconductive electrical charge through or around the logo. In thisembodiment the contrast may be achieved by providing an antistatic layerwith a colored dye or pigment or in the case of some materials such aspolythiophene, polyanaline or other conductive material that arenaturally colored as the background conducting region and the logo orindicia may not be printed thus having the color of the article orsupport substrate. In should also be noted that the logo or indicia maybe printed with the same conducting material as the backgroundconducting region but at a different coverage so as to provide someconductivity but at the same time have sufficient density difference asto make the logo visible. When patterns of conductive materials areprinted on supports, it may be desirable to have a transparent backsideflange layer.

For the purpose of clarification, as used in this application “light” isthe only type of electromagnetic radiation that is visible to the humaneye. Other types of radiation, such as “infrared radiation” are notvisible to the human eye because they have different wavelengths thanlight. “Light” has a wavelength range of 400 nm to 700 nm, which makesit visible to the human eye. Infrared radiation has a wavelength rangebeginning above 700 nm, generally at 800 nm which makes it invisible tothe human eye, that is, not visible to the human eye under daylightilluminance. Similarly, ultraviolet radiation has a wavelength that isless than 400 nm, making it invisible to the human eye, that is, notvisible to the human eye under daylight illuminance. Whenelectromagnetic radiation of the appropriate wavelength range is appliedto the substrate or support, the areas imprinted with conductivematerials not visible to the human eye under daylight illuminance willrespond by emitting electromagnetic radiation. The wavelength range ofthe emitted radiation is dependent on the specific characteristics ofthe materials used.

For a particular conductive material not visible to the human eye underdaylight illuminance, there is a specific wavelength range ofabsorbtivity and reflectance. The source of illuminance is matched tothe absorptivity of the pattern of the conductive materials and adetector is matched to its reflectivity. The conductive materials may beadded to inks. Examples of solvent based inks include nitrocellulosemaleic, nitrocellulose polyamide, nitrocellulose acrylic, nitrocelluloseurethane, chlorinated rubber, vinyl, acrylic, alcohol soluble acrylic,cellulose acetate acrylic styrene, and other synthetic polymers.Examples of water based inks include acrylic emulsion, maleic resindispersion styrene-maleic anhydride resins, and other syntheticpolymers. Examples of radiation cured inks include ultraviolet andelectron beam inks. The preferred ink systems for printing patterns ofconductive materials are water based inks and radiation cured inks,because of the need to reduce volatile organic compounds associated withsolvent based ink systems. Inks not visible to the human eye underdaylight illuminance, as they are transparent, may be applied to thebackside film support without altering the physical appearance of anydesigns on the support. It may be necessary in some formulations toadjust the refractive index of the antistat layer or the base to moreclosely match each other. In this manner the degree of perception of theconductive materials used as an antistat will be miminized. Any materialcapable of adjusting the refractive index may be used to make theadjustment. These may include the selection of polymer binder, or theaddition of nano particles such as ZnO, TiO2, clays, fluropolymers andothers.

The conductive material may be applied to the support as is or it may bedispersed in a carrier material. The antistatic layer of the inventionis preferred to comprise a colloidal sol, which may or may not beelectrically conductive, to improve physical properties such asdurability, roughness, coefficient of friction, as well as to reducecost. The colloidal sol preferred in the present invention comprisesfinely divided inorganic particles in a liquid medium, preferably water.Most preferably the inorganic particles are metal oxide based. Suchmetal oxides include tin oxide, titania, antimony oxide, zirconia,ceria, yttria, zirconium silicate, silica, alumina, such as boehmite,aluminum modified silica, as well as other inorganic metal oxides ofGroup III and IV of the Periodic Table and mixtures thereof. Theselection of the inorganic metal oxide sol is dependent on the ultimatebalance of properties desired as well as cost. Inorganic particles suchas silicon carbide, silicon nitride and magnesium fluoride when in solform are also useful for the present invention. The inorganic particlesof the sol have an average particle size less than 100 nm, preferablyless than 70 nm and most preferably less than 40 nm. A variety ofcolloidal sols useful in the present invention are commerciallyavailable from DuPont, Nalco Chemical Co., and Nyacol Products Inc.

The weight % of the inorganic particles of the aforesaid sol arepreferred to be at least 5% and more preferred to be at least 10% of thedried antistatic layer of the invention to achieve the desired physicalproperties.

The antistatic layer of the invention may also include a suitablepolymeric carrier, also referred to herein as a binder, to achievephysical properties such as adhesion, abrasion resistance, backmarkretention and others. Polymers are often used to promote adhesion of theconductive material to a base substrate or support material. They mayalso be useful in providing sufficient volume or bulk to make thecoating or printing method work within it design range. Polymers mayalso provide enhanced functionality to the antistatic layer such asscratch or abrasion resistance, proper sliding friction to optimizecoefficient of friction and other uses. The polymeric binder or carriercan be any polymer depending on the specific need. The carrier or binderpolymer can be one or more of a water soluble polymer, a hydrophiliccolloid or a water insoluble polymer, latex or dispersion. Particularpreference is given to polymers selected from the group of polymers andinterpolymers prepared from ethylenically unsaturated monomers such asstyrene, styrene derivatives, acrylic acid or methacrylic acid and theirderivatives, olefins, chlorinated olefins, (meth)acrylonitriles,itaconic acid and its derivatives, maleic acid and its derivatives,vinyl halides, vinylidene halides, vinyl monomer having a primary amineaddition salt, vinyl monomer containing an aminostyrene addition saltand others. Also included are carrier polymers such as polyurethanes andpolyesters. Particularly preferred carrier or binder polymers arepolymeric film-forming binder having a peel strength of 200 g or greateron a polypropylene surface, as disclosed in U.S. Pat. No. 6,171,769, orpolymeric film-forming binders of an interpolymer of a primary amineaddition salt, having a peel strength of 200 g or greater, as disclosedin U.S. Pat. No. 6,077,656, because of their excellent adhesioncharacteristics. Typically, the conductive material may comprise from 15to 85% weight of the antistatic layer. The carrier polymer maypreferably comprise from 15 to 85% by weight of the antistatic layer.

If formed by thermal processing, the polymeric binder or carrier may beany of the thermally processable polymers disclosed in U.S. Pat. Nos.6,197,486, 6,197,486, 6,207,361, 6,436,619, 6,465,140 and 6,566,033 andincorporated herein by reference. Suitable classes of thermoplasticpolymers preferred for this invention can include polymers of alpha-betaunsaturated monomers, polyesters, polyamides, polycarbonates, cellulosicesters, polyvinyl resins, polysulfonamides, polyethers, polyimides,polyurethanes, polyphenylenesulfides, polytetrafluoroethylene,polyacetals, polysulfonates, polyester ionomers, and polyolefinionomers. Interpolymers and/or mixtures of these polymers can also beused. Illustrative of polymers of alpha-beta unsaturated monomers, whichare suitable for use in this invention include polymers of ethylene,propylene, hexene, butene, octene, vinylalcohol, acrylonitrile,vinylidene halide, salts of acrylic acid, salts of methacrylic acid,tetrafluoroethylene, chlorotrifluoroethylene, vinyl chloride, andstyrene. Interpolymers and/or mixtures of these aforementioned polymerscan also be used in the present invention. Most preferred polymers fromthis category include polyethylene, polypropylenes and polystyrenestogether with their interpolymers and/or mixtures, because of their costand mechanical properties.

Other carrier polymers utilized in the invention can be any suitablethermoplastic polymer. Suitable classes of thermoplastic polymerspreferred for this invention may include polymers of alpha-betaunsaturated monomers, polyesters, polyamides, polycarbonates, cellulosicesters, polyvinyl resins, polysulfonamides, polyethers, polyimides,polyurethanes, polyphenylenesulfides, polytetrafluoroethylene,polyacetals, polysulfonates, polyester ionomers, and polyolefinionomers. Interpolymers and/or mixtures of these polymers can also beused. Polymers of alpha-beta unsaturated monomers, which are suitablefor use in this invention, may include polymers of ethylene, propylene,hexene, butene, octene, vinylalcohol, acrylonitrile, vinylidene halide,salts of acrylic acid, salts of methacrylic acid, tetrafluoroethylene,chlorotrifluoroethylene, vinyl chloride, and styrene. Interpolymersand/or mixtures of these aforementioned polymers can also be used in thepresent invention. Most preferred polymers from this category includepolypropylenes and polystyrenes together with their interpolymers and/ormixtures, because of their cost and mechanical properties.

Polyesters which are suitable for use as carrier polymers in thisinvention may include those which are derived from the condensation ofaromatic, cycloaliphatic, and aliphatic diols with aliphatic, aromaticand cycloaliphatic dicarboxylic acids and may be cycloaliphatic,aliphatic or aromatic polyesters. Useful cycloaliphatic, aliphatic andaromatic polyesters, which can be utilized in the practice of theirinvention, may include poly(ethylene terephthalate),poly(cyclohexlenedimethylene), terephthalate) poly(ethylene dodecate),poly(butylene terephthalate), poly(ethylene naphthalate),poly(ethylene(2,7-naphthalate)), poly(methaphenylene isophthalate),poly(glycolic acid), poly(ethylene succinate), poly(ethylene adipate),poly(ethylene sebacate), poly(decamethylene azelate), poly(ethylenesebacate), poly(decamethylene adipate), poly(decamethylene sebacate),poly(dimethylpropiolactone), poly(para-hydroxybenzoate), poly(ethyleneoxybenzoate), poly(ethylene isophthalate), poly(tetramethyleneterephthalate, poly(hexamethylene terephthalate), poly(decamethyleneterephthalate), poly(1,4-cyclohexane dimethylene terephthalate) (trans),poly(ethylene 1,5-naphthalate), poly(ethylene 2,6-naphthalate),poly(1,4-cyclohexylene dimethylene terephthalate) (cis), andpoly(1,4-cyclohexylene dimethylene terephthalate (trans).

Polyester compounds prepared from the condensation of a diol and anaromatic dicarboxylic acid is preferred for use in this invention.Useful aromatic carboxylic acids may include terephthalic acid,isophthalic acid and a o-phthalic acid, 1,3-napthalenedicarboxylic acid,1,4 napthalenedicarboxylic acid, 2,6-napthalenedicarboxylic acid,2,7-napthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid,4,4′-diphenysulfphone-dicarboxylic acid,1,1,3-trimethyl-5-carboxy-3-(p-carboxyphenyl)-idane, diphenyl ether4,4′-dicarboxylic acid, and bis-p(carboxy-phenyl) methane. Of theaforementioned aromatic dicarboxylic acids, those based on a benzenering (such as terephthalic acid, isophthalic acid, orthophthalic acid)are preferred. Terephthalic acid is a particularly preferred acidprecursor.

Preferred polyesters may include poly(ethylene terephthalate),poly(butylene terephthalate), poly(1,4-cyclohexylene dimethyleneterephthalate), poly(ethylene naphthalate) and interpolymers and/ormixtures thereof. Among these polyesters of choice, poly(ethyleneterephthalate), which may be modified by small amounts of othermonomers, is most preferred.

Polyamides, which are suitable for use as carrier polymers in thisinvention, may include synthetic linear polycarbonamides characterizedby the presence of recurring carbonamide groups as an integral part ofthe polymer chain, which are separated from one another by at least twocarbon atoms. Polyamides of this type include polymers, generally knownin the art as nylons, obtained from diamines and dibasic acids havingthe recurring unit represented by the general formula:—NHCOR¹COHNR²—in which R¹ is an alkylene group of at least 2 carbon atoms, preferablyfrom 2 to 11 or arylene having at least 6 carbon atoms, preferably 6 to17 carbon atoms; and R² is selected from R¹ and aryl groups. Also,included are copolyamides and terpolyamides obtained by known methods,for example, by condensation of hexamethylene diamine and a mixture ofdibasic acids consisting of terephthalic acid and adipic acid.Polyamides of the above description are well-known in the art andinclude, for example, the copolyamide of 30% hexamethylene diammoniumisophthalate and 70% hexamethylene diammonium adipate,poly(hexamethylene adipamide) (nylon 6,6), poly(hexamethylenesebacamide) (nylon 6, 10), poly(hexamethylene isophthalamide),poly(hexamethylene terephthalamide), poly(heptamethylene pimelamide)(nylon 7,7), poly(octamethylene suberamide) (nylon 8,8),poly(nonamethylene azelamide) (nylon 9,9) poly (decamethylene azelamide)(nylon 10,9), poly(decamethylene sebacamide) (nylon 10,10),poly(bis(4-amino cyclohexyl)methane-1,10-decane-carboxamide)),poly(m-xylylene adipamide), poly(p-xylene sebacamide),poly(2,2,2-trimethyl hexamethylene terephthalamide), poly(piperazinesebacamide), poly(p-phenylene terephthalamide), and poly(metaphenyleneisophthalamide).

Other useful polyamides are those formed by polymerization of aminoacids and derivatives thereof, as for example lactams. Useful polyamidesmay include poly(4-aminobutyric acid) (nylon 4), poly(6-aminohexanoicacid) (nylon 6), poly(7-aminoheptanoic acid) (nylon 7),poly(8-aminooctanoic acid) (nylon 8), poly(9-aminononanoic acid) (nylon9), poly(10-amino-decanoic acid) (nylon 10), poly(11-aminoundecanoicacid) (nylon 11), and poly(12-aminododecanoic acid) (nylon 12). The mostpreferred polyamides include poly(caprolactam), poly(12-aminododecanoicacid), poly(hexamethylene adipamide), poly(m-xylylene adipamide),poly(6-aminohexanoic acid), and interpolymers and/or mixtures thereof.

Suitable cellulose esters may include cellulose nitrate, cellulosetriacetate, cellulose diacetate, cellulose acetate propionate, celluloseacetate butyrate, and interpolymers and/or mixtures thereof. Apolycarbonate preferred for use in this invention is bisphenol-Apolycarbonate. Useful polyvinyl resins may include polyvinyl chloride,poly (vinyl acetal) and interpolymers and/or mixtures thereof.

The antistatic layer of the invention may include other optionalcomponents. Such optional components may include compatibilizers,nucleating agents, fillers, plasticizers, impact modifiers, chainextenders, colorants, lubricants, surfactants and coating aids, otherantistatic conductive agents, onium salts, pigments such as titaniumoxide, zinc oxide, talc, calcium carbonate, barium sulfate, clay,dispersants such as fatty amides, (for example, stearamide), metallicsalts of fatty acids, for example, zinc stearate, magnesium stearate,calcium stearate, dyes such as ultramarine blue, cobalt violet,antioxidants, fluorescent whiteners, ultraviolet absorbers, fireretardants, matte particles or roughening agents, such as silica,titanium dioxide, talc, barium sulfate, clay, and alumina, cross linkingagents, solvents and cosolvents, and voiding agents. These optionalcomponents and appropriate amounts are well known in the art and can bechosen according to need.

The antistatic layer of the present invention may be applied to thesubstrate or support in a manner capable of producing a pattern havingareas of coverage and areas without coverage. The pattern should providea continuous conductive pathway and/or a network of conductive pathwayson, around, or in the substrate or support. The pattern may form asimple grid pattern or any other interconnected labyrinthine patterncomprising at least one line or a series of continuous segments, such asdots, lines or other shapes. For example, shapes may includeinterconnecting square, circles, triangles, or butterflies. The patternmay also form a gradient pattern having areas of differing coverage. Ina preferred embodiment, the areas of higher coverage demonstrate aresistivity of less than 10¹³ ohm/sq and the areas of lower coveragedemonstrate a resistivity of greater than or equal to 10¹³ ohm/sq.

The patterns useful in this invention may also form traditional logos toprovide the consumer with brand recognition, or machine readable indiciaon the back of the support, which allow for planar metrology of web andsheet material without contact. The pattern used in this invention maybe printed, coated or embossed. The pattern may form a character, or alogo with at least one character. In other useful embodiments, thepattern, such as characters, may comprise at least one member selectedfrom the group consisting of letters, pictures, numbers, symbols, andwords. An additional useful embodiment of this invention would be toapply ink or colored material containing the conductive material to theembossed pattern area or to the background area and not the pattern areain order to provide a pattern easier to view and which is less angulardependant when viewing. Such ink or colored solution containing theconductive materials may be aqueous or solvent-based.

“Planar metrology” as used in this application, is defined as point topoint measurement of length through the use of predetermined coordinatesystems. In a preferred case, rectangular coordinates are used forlinear metrology. “Linear Metrology” as used in this application isdefined to be the straight line measurement between two points. In webor sheet material applications, both machine and cross machine directionmeasurements are typically employed. Of particular interest are machinedirection measurements. The use of patterns not visible to the human eyeunder daylight illuminance may be applied to linear metrology of highspeed webs without surface contact. The patterns of conductive materialmay also be analyzed against time to evaluate and control web speed andlinear movement. Patterns of conductive indicia may further provide theaccurate mapping of potentially defective areas of a substrate orsupport, and allow for the precise and rapid locating of such areas forremoval. The use of different non-uniformly spaced patterns may be usedto encode a variety of measurements in either the cross web or machinedirection. The spacing of the pattern indicia will desirably match thecapabilities of the equipment that applies and senses the pattern. Apractical range of spacing for either uniform or non-uniform spacing isfrom 1 mm to 1 m.

The antistatic layer may be a coated or printed layer. The layer may beapplied onto the substrate or support by conventional coating andprinting means commonly used in this art. Coating methods may include,but are not limited to, extrusion coating, blade coating, wound wire rodcoating, slot coating, hopper and slide hopper coating, gravure coating,curtain coating, spray coating, or inkjet coating. Printing methods mayinclude gravure printing, offset printing, thermography, screenprinting, electrophotography and other techniques. Some of these methodsallow for simultaneous coatings of layers, which is preferred from amanufacturing economic perspective. Simultaneous coating may includesimultaneous or consecutive extrusion coating or combinations thereof.

The surface on which the antistatic layer is deposited may be treatedfor improved adhesion by any of the means known in the art, such as acidetching, flame treatment, corona discharge treatment, glow dischargetreatment or may be coated with a suitable primer layer. Coronadischarge treatment is a preferred means for adhesion promotion. Theantistatic layer may also be applied over an adhesion promoting primerlayer of an interpolymer of a primary amine addition salt, as disclosedin U.S. Pat. No. 6,120,979.

The antistatic layer is applied to a support. The support may be eitheropaque or transparent. In one preferred embodiment, the supportspreferably comprise opaque and/or transparent film-based output andcapture supports. Opaque supports include plain paper, coated paper,resin-coated paper such as polyolefin-coated paper, synthetic paper,photographic paper support, melt-extrusion-coated paper,polyolefin-laminated paper, such as biaxially oriented supportlaminates, web materials, and sheet materials. In a preferredembodiment, the support comprises a support for an imaging element,which has an opacity of greater than 60. The support may also consist ofmicroporous materials such as polyethylene polymer-containing materialsold by PPG Industries, Inc., Pittsburgh, Pa. under the trade name ofTeslin®, Tyvek® synthetic paper (DuPont Corp.), impregnated paper suchas Duraform®, and OPPalyte® films (Mobil Chemical Co.) and othercomposite films listed in U.S. Pat. No. 5,244,861. Commerciallyavailable oriented and unoriented polymer films, such as opaquebiaxially oriented polypropylene or polyester, may also be utilized.Such supports may contain pigments, air voids or foam voids to enhancetheir opacity. Transparent supports include glass, cellulosederivatives, such as a cellulose ester, cellulose triacetate, cellulosediacetate, cellulose acetate propionate, cellulose acetate butyrate,polyesters, such as poly(ethylene terephthalate), poly(ethylenenaphthalate), poly-1,4-cyclohexanedimethylene terephthalate,poly(butylene terephthalate), and copolymers thereof, polyimides,polyamides, polycarbonates, polystyrene, polyolefins, such aspolyethylene or polypropylene, polysulfones, polyacrylates, polyetherimides, and mixtures thereof. The term as used herein, “transparent”means the ability to pass visible radiation without significantdeviation or absorption. In a preferred embodiment, the element has a %transmission of greater than 80%.

The imaging element support used in the invention may have a thicknessof from 50 to 500 μm, preferably from 75 to 350 μm. Antioxidants,brightening agents, antistatic or conductive agents, plasticizers andother known additives may be incorporated into the support, if desired.In one preferred embodiment, the element has an L* of greater than 80and a b* of from 0 to −6.0.

In one preferred embodiment, the support may comprise a paper core thathas adhered thereto at least one flange layer. The paper may come from abroad range of papers, from high end papers, such as photographic paperto low end papers, such as newsprint. In a preferred embodiment,photographic paper is employed. The paper may be made on a standardcontinuous fourdrinier wire machine or on other modern paper formers.Any pulps known in the art to provide paper may be used in thisinvention. Bleached hardwood chemical kraft pulp is preferred, as itprovides brightness, a smooth starting surface, and good formation whilemaintaining strength. Paper cores useful to this invention are ofcaliper from 50 μm to 230 μm, preferably from 100 μm to 190 μm becausethen the overall element thickness is in the range preferred bycustomers for imaging element and processes in existing equipment. Theymay be “smooth” as to not interfere with the viewing of images. Chemicaladditives to impart hydrophobicity (sizing), wet strength, and drystrength may be used as needed. Inorganic filler materials such as TiO₂,talc, mica, BaSO4 and CaCO₃ clays may be used to enhance opticalproperties and reduce cost as needed. Dyes, biocides, and processingchemicals may also be used as needed. The paper may also be subject tosmoothing operations such as dry or wet calendering, as well as tocoating through an in-line or an off-line paper coater.

In another embodiment, the support comprises a synthetic paper,preferably cellulose-free, having a polymer core that has adheredthereto at least one flange layer. The polymer core comprises ahomopolymer such as a polyolefin, polystyrene, polyester,polyvinylchloride or other typical thermoplastic polymers; theircopolymers or their blends thereof; or other polymeric systems likepolyurethanes, polyisocyanurates. These materials may or may not havebeen expanded either through stretching resulting in voids or throughthe use of a blowing agent to consist of two phases, a solid polymermatrix, and a gaseous phase. Other solid phases may be present in theform of fillers that are of organic (polymeric, fibrous) or inorganic(glass, ceramic, metal) origin. The fillers may be used for physical,optical (lightness, whiteness, and opacity), chemical, or processingproperty enhancements of the core. Microvoided composite biaxiallyoriented sheets may be utilized and are conveniently manufactured bycoextrusion of the core and surface layers, followed by biaxialorientation, whereby voids are formed around void-initiating materialcontained in the core layer. Such composite sheets are disclosed in, forexample, U.S. Pat. Nos. 4,377,616; 4,758,462 and 4,632,869, thedisclosure of which is incorporated for reference.

“Void” is used herein to mean devoid of added solid and liquid matter,although it is likely the “voids” contain gas. The void-initiatingparticles, which remain in the finished packaging sheet core, should befrom 0.1 to 10 microns in diameter and preferably round in shape toproduce voids of the desired shape and size. The size of the void isalso dependent on the degree of orientation in the machine andtransverse directions. Ideally, the void would assume a shape that isdefined by two opposed, and edge contacting, concave disks. In otherwords, the voids tend to have a lens-like or biconvex shape. The voidsare oriented so that the two major dimensions are aligned with themachine and transverse directions of the sheet. The Z-direction axis isa minor dimension and is roughly the size of the cross diameter of thevoiding particle. The voids generally tend to be closed cells, and thusthere is virtually no path open from one side of the voided-core to theother side through which gas or liquid may traverse.

In another embodiment, the support comprises a synthetic paper,preferably cellulose-free, having a foamed polymer core or a foamedpolymer core that has adhered thereto at least one flange layer. Thepolymers described for use in a polymer core may also be employed inmanufacture of the foamed polymer core layer, carried out throughseveral mechanical, chemical, or physical means. Mechanical methodsinclude whipping a gas into a polymer melt, solution, or suspension,which then hardens either by catalytic action or heat or both, thusentrapping the gas bubbles in the matrix. Chemical methods include suchtechniques as the thermal decomposition of chemical blowing agentsgenerating gases such as nitrogen or carbon dioxide by the applicationof heat or through exothermic heat of reaction during polymerization.Physical methods include such techniques as the expansion of a gasdissolved in a polymer mass upon reduction of system pressure; thevolatilization of low-boiling liquids such as fluorocarbons or methylenechloride, or the incorporation of hollow microspheres in a polymermatrix. The choice of foaming technique is dictated by desired foamdensity reduction, desired properties, and manufacturing process.Preferably, the foamed polymer core comprises a polymer expanded throughthe use of a blowing agent.

In a preferred embodiment of this invention polyolefins such aspolyethylene and polypropylene, their blends and their copolymers areused as the matrix polymer in the foamed polymer core along with achemical blowing agent such as sodium bicarbonate and its mixture withcitric acid, organic acid salts, azodicarbonamide, azobisformamide,azobisisobutyroInitrile, diazoaminobenzene, 4,4′-oxybis(benzene sulfonylhydrazide) (OBSH), N,N′-dinitrosopentamethyltetramine (DNPA), sodiumborohydride, and other blowing agent agents well known in the art. Thepreferred chemical blowing agents would be sodium bicarbonate/citricacid mixtures, azodicarbonamide; though others may also be used. Thesefoaming agents may be used together with an auxiliary foaming agent,nucleating agent, and a cross-linking agent.

The flange layers, which may be applied to the core of the support, maybe chosen to satisfy specific requirements of flexural modulus, caliper,surface roughness, and optical properties such as colorimetry andopacity. The flange members may be formed integral with the core bymanufacturing the core with a flange skin sheet or the flange may belaminated to the core material. The integral extrusion of flange memberswith the core is preferred for cost. The lamination technique allows awider range of properties and materials to be used for the skinmaterials.

Imaging elements are constrained to a range in stiffness and caliper. Atstiffness below a certain minimum stiffness, there is a problem with theelement in print stackability and print conveyance during transportthrough photofinishing equipment, particularly high speedphotoprocessors. It is believed that there is a minimum cross directionstiffness of 60 mN required for effective transport throughphotofinishing equipment. At stiffness above a certain maximum, there isa problem with the element in cutting, punching, slitting, and choppingduring transport through photofinishing equipment. It is believed thatthere is a maximum machine direction stiffness of 300 mN for effectivetransport through photofinishing equipment. The caliper of the imagingelement may be constrained from 75 μm to 350 μm for reasons relating totransport through photofinishing equipment.

Preferred ranges of core caliper and modulus and flange caliper andmodulus follow: the preferred caliper of the polymer core useful withthe invention ranges from 65 μm to 340 μm, the caliper of the flangesheets useful with the invention ranges from 10 μm to 175 μm, themodulus of the core useful with the invention ranges from 30 MPa to 1000MPa, and the modulus of the flange sheets useful with the inventionranges from 690 to 5516 MPa. In each case, the above range is preferredbecause of (a) consumer preference, (b) manufacturability, and (c)materials selection. It is noted that the final choice of flange andcore materials, modulus, and caliper will be a subject of the targetoverall element stiffness and caliper.

The flange sheets used comprise thermoplastic polymers. Suitable classesof thermoplastic polymers for blending include polyolefins, polyesters,polyamides, polycarbonates, cellulosic esters, polystyrene, polyvinylresins, polysulfonamides, polyethers, polyimides, polyvinylidenefluoride, polyurethanes, polyphenylenesulfides, polytetrafluoroethylene,polyacetals, polysulfonates, polyester ionomers, and polyolefinionomers. Copolymers and/or mixtures of these polymers may be used.Polypropylene and polyethylene are preferred, as they are low in costand have desirable strength properties.

Suitable polyolefins include polypropylene, polyethylene,polymethylpentene, and mixtures thereof. Polyolefin copolymers,including copolymers of propylene and ethylene such as hexene, buteneand octene are also useful. Polypropylenes are preferred because theyare low in cost and have good strength and surface properties.

Suitable polyesters include those produced from aromatic, aliphatic orcycloaliphatic dicarboxylic acids of 4–20 carbon atoms and aliphatic oralicyclic glycols having from 2–24 carbon atoms. Examples of suitabledicarboxylic acids include terephthalic, isophthalic, phthalic,naphthalene dicarboxylic acid, succinic, glutaric, adipic, azelaic,sebacic, fumaric, maleic, itaconic, 1,4-cyclohexanedicarboxylic,sodiosulfoisophthalic and mixtures thereof. Examples of suitable glycolsinclude ethylene glycol, propylene glycol, butanediol, pentanediol,hexanediol, 1,4-cyclohexanedimethanol, diethylene glycol, otherpolyethylene glycols and mixtures thereof. Such polyesters are wellknown in the art and may be produced by known techniques, for example,those described in U.S. Pat. Nos. 2,465,319 and 2,901,466. Preferredcontinuous matrix polyesters are those having repeat units fromterephthalic acid or naphthalene dicarboxylic acid and at least oneglycol selected from ethylene glycol, 1,4-butanediol and1,4-cyclohexanedimethanol. Poly(ethylene terephthalate), which may bemodified by small amounts of other monomers, is especially preferred.Other suitable polyesters include liquid crystal copolyesters formed bythe inclusion of suitable amount of a co-acid component such as stilbenedicarboxylic acid. Examples of such liquid crystal copolyesters arethose disclosed in U.S. Pat. Nos. 4,420,607, 4,459,402 and 4,468,510.

Useful polyamides include nylon 6, nylon 66, and mixtures thereof.Copolymers of polyamides are also suitable continuous phase polymers. Anexample of a useful polycarbonate is bisphenol-A polycarbonate.Cellulosic esters suitable for use as the continuous phase polymer ofthe composite sheets include cellulose nitrate, cellulose triacetate,cellulose diacetate, cellulose acetate propionate, cellulose acetatebutyrate, and mixtures or copolymers thereof. Useful polyvinyl resinsinclude polyvinyl chloride, poly(vinyl acetal), and mixtures thereof.Copolymers of vinyl resins may also be utilized.

The flange layers may also include other additives. These may includefiller materials such as titanium dioxide and calcium carbonate andcolorants, pigments, dyes and/or optical brighteners or other additivesknown to those skilled in the art. Some of the commonly used inorganicfiller materials are talc, clays, calcium carbonate, magnesiumcarbonate, barium sulfate, mica, aluminum hydroxide (trihydrate),wollastonite, glass fibers and spheres, silica, various silicates, andcarbon black. Some of the organic fillers used are wood flour, jutefibers, sisal fibers, or polyester fibers. The preferred fillers aretalc, mica, and calcium carbonate because they provide excellent modulusenhancing properties. The fillers may be in the flange or an overcoatlayer, such as polyethylene. Generally, base materials for color printimaging materials are white, possibly with a blue tint as a slight blueis preferred to form a preferred white look to whites in an image. Anysuitable white pigment may be incorporated in the support such as, forexample, titanium dioxide, zinc oxide, zinc sulfide, zirconium dioxide,white lead, lead sulfate, lead chloride, lead aluminate, lead phthalate,antimony trioxide, white bismuth, tin oxide, white manganese, whitetungsten, and combinations thereof. The preferred pigment is titaniumdioxide. In addition, suitable optical brightener may be employed in thepolyolefin layer including those described in Research Disclosure, Vol.No. 308, December 1989, Publication 308119, Paragraph V, page 998.

In addition, it may be desirable to use various additives such asantioxidants, stiffness enhancing agents, slip agents, or lubricants,and light stabilizers in the synthetic elements, especially syntheticplastic elements, as well as biocides in the paper elements. Theseadditives are added to improve, among other things, the dispersibilityof fillers and/or colorants, as well as the thermal and color stabilityduring processing and the manufacturability and the longevity of thefinished article. For example, polyolefin coatings may containantioxidants such as 4,4′-butylidene-bis(6-tert-butyl-meta-cresol),di-lauryl-3,3′-thiopropionate, N-butylated-p-aminophenol,2,6-di-tert-butyl-p-cresol, 2,2-di-tert-butyl-4-methyl-phenol,N,N-disalicylidene-1,2-diaminopropane,tetra(2,4-tert-butylphenyl)-4,4′-diphenyl diphosphonite, octadecyl3-(3′,5′-di-tert-butyl-4′-hydroxyphenyl propionate), combinations of theabove, lubricants, such as higher aliphatic acid metal salts such asmagnesium stearate, calcium stearate, zinc stearate, aluminum stearate,calcium palmitate, zirconium octylate, sodium laurate, and salts ofbenzoic acid such as sodium benzoate, calcium benzoate, magnesiumbenzoate and zinc benzoate; light stabilizers such as hindered aminelight stabilizers (HALS), of which a preferred example ispoly{[6-[(1,1,3,3-tetramethylbutylamino}-1,3,5-triazine-4-piperidinyl)-imino]-1,6-hexanediyl[{2,2,6,6-tetramethyl-4-piperdinyl)imino]} (Chimassorb® 944 LD/FL),7-Oxa-3,20-diazadispiro[5.1.11.2]heneicosan-21-one,2,2,4,4-tetramethyl-20-(oxiranylmethyl)-, homopolymer (Hostavin® N30).

The flange layers, which may be applied to the foam core, may beunoriented or may have been stretched and oriented. They may be filledwith suitable filler materials to further increase the modulus of thepolymer and enhance other properties such as opacity and smoothness.

In one preferred embodiment of the invention the flange layer may be abiaxially oriented sheet. The thickness of the biaxially oriented sheetshould be from 5 to 150 microns. Below 5 microns, the sheets may not bethick enough to minimize any inherent non-planarity in the support andwould be more difficult to manufacture. At thicknesses higher than 150microns, little improvement in either surface smoothness or mechanicalproperties is seen, and so there is little justification for the furtherincrease in cost for extra materials.

The biaxially oriented flange layers may be transparent for viewingobjects through the back sheet or addenda, also referred to herein asadditives, may be added to the biaxially oriented flange layers to colorand opacify these layers.

The support may be produced by any method know in the art for producingimaging supports. A preferred embodiment is extrusion of the antistaticlayer on to the core layer (paper or synthetic core, for example). Thismay entail either monolayer extrusion or coextrusion of additionallayers. Extrusion laminating may be carried out by bringing together thepolymeric flange sheets and the core with application of an adhesivebetween them.

In one embodiment utilizing oriented sheets, most preferably biaxiallyoriented sheets, the coextrusion, quenching, orienting, and heat settingof these biaxially oriented sheets may be effected by any process whichis known in the art for producing oriented sheet, such as by a flatsheet process or a bubble or tubular process, as in, for example, U.S.Pat. No. 4,764,425. The flat sheet process involves extruding orcoextruding the blend through a slit die and rapidly quenching theextruded or coextruded support upon a chilled casting drum so that thepolymer component(s) of the sheet are quenched below theirsolidification temperature. The quenched sheet is then biaxiallyoriented by stretching in mutually perpendicular directions at atemperature above the glass transition temperature of the polymer(s).The sheet may be stretched in one direction and then in a seconddirection or may be simultaneously stretched in both directions. Afterthe sheet has been stretched, it is heat set by heating to a temperaturesufficient to crystallize the polymers while restraining to some degreethe sheet against retraction in both directions of stretching.

To promote adhesion, an adhesive may be applied to either the flangesheets or the core prior to their being brought into a nip. In apreferred form, the adhesive is applied into the nip simultaneously withthe flange sheets and the core. The adhesive may be any suitablematerial that does not have a harmful effect upon the element. Thepreferred materials are melt extrudable polymers but other solutionbased adhesives may also be used. These may include both aqueous andsolvent based adhesive and may be either pressure sensitive or thermalactivated adhesives. Adhesive composition may be selected from the groupconsisting of natural rubber, synthetic rubber, acrylics, acryliccopolymers, vinyl polymers, vinyl acetate-, urethane, acrylate-typematerials, copolymer mixtures of vinyl chloride-vinyl acetate,polyvinylidene, vinyl acetate-acrylic acid copolymers, stryenebutadiene, carboxylated styrene butadiene copolymers, ethylenecopolymers, polyvinyl alcohol, polyesters and copolymers, cellulosic andmodified cellulosic, starch and modified starches compounds, epoxies,polyisocyanate, polyimides. A preferred adhesive material is a 20%/80%blend of an extrusion grade low density polyethylene melt extruded at 12g/m² and an acrylate modified copolymer (Dupont Bynel) and that helpspromote adhesion of polyester compounds to other materials such aspaper. A blend with polyethylene also helps to improve adhesion topolyethylene.

In a preferred embodiment, the layer of adhesive resin may also comprisean ethylene polymer blended with a metallocene catalyzed polyolefinplastomer, ionomer, ethylene vinyl acetate copolymer, ethylene methylmethacrylate copolymer, ethylene ethyl acrylate copolymer, ethylenemethyl acrylate copolymer, ethylene acrylic acid copolymer, ethyleneethyl acrylate maleic anhydride copolymer, or ethylene methacrylic acidcopolymer.

Metallocene catalyzed polyolefin plastomers are preferred forbonding-oriented polymer sheets to photographic base paper because theyoffer a combination of excellent adhesion to smooth biaxially orientedpolymer sheets, are easily melt extruded using conventional extrusionequipment and are low in cost when compared to other adhesive resins.Metallocenes are a class of highly active olefin catalysts that are usedin the preparation of polyolefin plastomers. These catalysts,particularly those based on group IVB transition metals such aszirconium, titanium, and hafnium, show extremely high activity inethylene polymerization. Various forms of the catalyst system of themetallocene type may be used for polymerization to prepare the polymersused for bonding biaxially oriented polyolefin sheets to cellulosepaper. Forms of the catalyst system include but are not limited to thoseof homogeneous, supported catalyst type, high pressure process or aslurry or a solution polymerization process. The metallocene catalystsare also highly flexible in that, by manipulation of catalystcomposition and reaction conditions, they may be made to providepolyolefins with controllable molecular weights. Suitable polyolefinsinclude polypropylene, polyethylene, polymethylpentene, polystyrene,polybutylene and mixtures thereof. Development of these metallocenecatalysts for the polymerization of ethylene is found in U.S. Pat. No.4,937,299 (Ewen et al.) The most preferred metallocene catalyzedcopolymers are very low density polyethylene (VLDPE) copolymers ofethylene and a C₄ to C₁₀ alpha monolefin, most preferably copolymers andterpolymers of ethylene and butene-1 and hexene-1. The melt index of themetallocene catalyzed ethylene plastomers preferably fall in a range offrom 2.5 g/10 min to 27 g/10 min. The density of the metallocenecatalyzed ethylene plastomers preferably falls in a range of from 0.8800to 0.9100. In one preferred embodiment, low density polyethylene(hereinafter referred to as LDPE) may be utilized with the metallocenecatalyzed ethylene plastomer. In general, the preferred range of LDPEblended is 10% to 80% by weight.

Addenda, also referred to herein as additives, may also be added to theadhesive layer. Any known material used in the art to improve theoptical performance of the system may be used. The use of TiO₂ ispreferred. During the lamination process, it is desirable to alsomaintain control of the tension of the flange sheets in order tominimize curl in the resulting laminated receiver support.

The imaging support, while described as having preferably at least twoor three layers—a core and a flange layer on at least one side, may alsobe provided with additional layers that may serve to change theproperties of the support. These might include layers to provide a vaporbarrier, to improve opacity, to control color or static, to make themheat sealable, or to improve the adhesion to the support or to thephotosensitive layers. Examples of this would be coating polyvinylidenechloride for heat seal properties. Further examples include flame,plasma, or corona discharge treatment to improve printability oradhesion.

Biaxially oriented sheets, while described as having preferably at leastone layer, may also be provided with additional layers that may serve tochange the properties of the biaxially oriented sheet. Such layers mightcontain tints, antistatic or conductive materials, or slip agents toproduce sheets of unique properties. Biaxially oriented sheets may beformed with surface layers, referred to herein as skin layers, whichwould provide an improved adhesion, or look to the support andphotographic element. The biaxially oriented extrusion may be carriedout with as many as 10 layers if desired to achieve some particulardesired property. The biaxially oriented sheet may be made with layersof the same polymeric material, or it may be made with layers ofdifferent polymeric composition. For compatibility, an auxiliary layermay be used to promote adhesion of multiple layers.

A preferred application of the invention is in imaging elements,including those utilizing photographic, electrophotographic,electrostatographic, photothermographic, migration,electrothermographic, dielectric recording, thermal dye transfer, inkjet and other types of imaging. A more preferred application of theinvention is in photographic imaging elements, particularly photographicpaper and other display products. Display products may include bothphotographic display products as well as flat panel-type displayproducts, for example, liquid crystal display products.

The article of the present invention may preferably comprise an imagingelement having at least one imaging layer. Preferably, the imaging layeris positioned on a support and comprises photosensitive silver halideimaging layer, an inkjet imaging layer, a thermal imaging layer, anelectrically modulated imaging layer, or an electrophotographic imaginglayer.

As used herein the phrase “imaging element” is a material that may beused as a imaging support for the transfer of images to the support bytechniques such as ink jet printing or thermal dye transfer as well as asupport for silver halide images. As used herein, the phrase“photographic element” is a material that utilizes photosensitive silverhalide in the formation of images.

Inks used to image the recording elements of the present invention arewell known in the art. The ink compositions used in inkjet printingtypically may be liquid compositions comprising a solvent or carrierliquid, dyes or pigments, humectants, organic solvents, detergents,thickeners, preservatives. The solvent or carrier liquid may be solelywater or may be water mixed with other water-miscible solvents such aspolyhydric alcohols. Inks in which organic materials such as polyhydricalcohols may be the predominant carrier or solvent liquid may also beused. Particularly useful are mixed solvents of water and polyhydricalcohols. The dyes used in such compositions may be typicallywater-soluble direct or acid type dyes. Such liquid compositions havebeen described extensively in the prior art including, for example, U.S.Pat. Nos. 4,381,946; 4,239,543; and 4,781,758, the disclosures of whichare hereby incorporated by reference.

When used as inkjet imaging media, the recording elements or mediatypically comprise a substrate or a support material having on at leastone surface thereof an ink-receiving or recording/recording orimage-forming layer. If desired, in order to improve the adhesion of theinkjet receiving or recording layer to the support, the surface of thesupport may be corona-discharge-treated prior to applying thesolvent-absorbing layer to the support or, alternatively, anundercoating, such as a layer formed from a halogenated phenol or apartially hydrolyzed vinyl chloride-vinyl acetate copolymer, may beapplied to the surface of the support. The inkjet receiving or recordinglayer may be preferably coated onto the support layer from water orwater-alcohol solutions at a dry thickness ranging from 3 to 75micrometers, preferably 8 to 50 micrometers.

Any known inkjet receiver layer may be used in combination with otherparticulate materials. For example, the ink receiving or recording layermay consist primarily of inorganic oxide particles such as silicas,modified silicas, clays, aluminas, fusible beads such as beads comprisedof thermoplastic or thermosetting polymers, non-fusible organic beads,or hydrophilic polymers such as naturally-occurring hydrophilic colloidsand gums such as gelatin, albumin, guar, xantham, acacia, chitosan,starches and their derivatives, derivatives of natural polymers such asfunctionalized proteins, functionalized gums and starches, and celluloseethers and their derivatives, and synthetic polymers such aspolyvinyloxazoline, polyvinylmethyloxazoline, polyoxides, polyethers,poly(ethylene imine), poly(acrylic acid), poly(methacrylic acid),n-vinyl amides including polyacrylamide and polyvinylpyrrolidone, andpoly(vinyl alcohol), its derivatives and copolymers, and combinations ofthese materials. Hydrophilic polymers, inorganic oxide particles, andorganic beads may be present in one or more layers on the substrate andin various combinations within a layer.

A porous structure may be introduced into ink receiving or recordinglayers comprised of hydrophilic polymers by the addition of ceramic orhard polymeric particulates, by foaming or blowing during coating, or byinducing phase separation in the layer through introduction ofnon-solvent. In general, it is preferred for the base layer to behydrophilic, but not porous. This may be especially true forphotographic quality prints, in which porosity may cause a loss ingloss. In particular, the ink receiving or recording layer may consistof any hydrophilic polymer or combination of polymers with or withoutadditives as is well known in the art.

If desired, the ink receiving or recording layer may be overcoated withan ink-permeable, anti-tack protective layer such as, for example, alayer comprising a cellulose derivative or a cationically-modifiedcellulose derivative or mixtures thereof. An especially preferredovercoat is polyβ-1,4-anhydro-glucose-g-oxyethylene-g-(2′-hydroxypropyl)-N,N-dimethyl-N-dodecylammoniumchloride. The overcoat layer may be non porous, but may be ink permeableand serves to improve the optical density of the images printed on theelement with water-based inks. The overcoat layer may also protect theink receiving or recording layer from abrasion, smudging, and waterdamage. In general, this overcoat layer may be present at a drythickness of from 0.1 to 5 μM, preferably from 0.25 to 3 μm.

In practice, various additives may be employed in the ink receiving orrecording layer and overcoat. These additives include surface activeagents such as surfactant(s) to improve coatability and to adjust thesurface tension of the dried coating, acid or base to control the pH,antistatic or conductive agents, suspending agents, antioxidants,hardening agents to cross-link the coating, antioxidants, UVstabilizers, light stabilizers. In addition, a mordant may be added insmall quantities (2%–10% by weight of the base layer) to improvewaterfastness. Useful mordants are disclosed in U.S. Pat. No. 5,474,843.

The layers, including the ink receiving or recording layer and theovercoat layer, may be coated by conventional coating means onto atransparent or opaque support material. Coating methods may include, butare not limited to, blade coating, wound wire rod coating, slot coating,slide hopper coating, gravure, curtain coating. Some of these methodsallow for simultaneous coatings of both layers, which is preferred froma manufacturing economic perspective.

The ink receiving or recording layer (IRL) may also contain varyinglevels and sizes of matting agents for the purpose of controlling gloss,friction, and/or fingerprint resistance, surfactants to enhance surfaceuniformity and to adjust the surface tension of the dried coating,mordanting agents, antioxidants, UV absorbing compounds, lightstabilizers.

The thermal dye image-receiving layer (hereinafter referred to as DRL)of receiving elements used with the invention may comprise, for example,a polycarbonate, a polyurethane, a polyester, polyvinyl chloride,poly(styrene-co-acrylonitrile), poly(caprolactone) or mixtures thereof.The dye image-receiving layer may be present in any amount that iseffective for the intended purpose. In general, good results have beenobtained at a concentration of from 1 to 10 g/m². An overcoat layer maybe further coated over the dye-receiving layer, such as described inU.S. Pat. No. 4,775,657 of Harrison et al.

Dye-donor elements that are used with dye-receiving elements used in theinvention conventionally comprise a support having thereon a dyecontaining layer. Any dye may be used in the dye-donor employed in theinvention provided it is transferable to the dye-receiving layer by theaction of heat. Especially good results have been obtained withsublimable dyes. Dye donors applicable for use in the present inventionare described, for example, in U.S. Pat. Nos. 4,916,112; 4,927,803 and5,023,228.

As noted above, dye-donor elements are used to form a dye transferimage. Such a process comprises image-wise-heating a dye-donor elementand transferring a dye image to a dye-receiving element as describedabove to form the dye transfer image.

In a preferred embodiment of the thermal dye transfer method ofprinting, a dye donor element is employed which compromises apoly-(ethylene terephthalate) support coated with sequential repeatingareas of cyan, magenta, and yellow dye, and the dye transfer steps aresequentially performed for each color to obtain a three-color dyetransfer image. Of course, when the process is only performed for asingle color, then a monochrome dye transfer image is obtained.

Thermal printing heads that may be used to transfer dye from dye-donorelements to receiving elements used with the invention are availablecommercially. There may be employed, for example, a Fujitsu Thermal Head(FTP-040 MCS001), a TDK Thermal Head F415 HH7-1089 or a Rohm ThermalHead KE 2008-F3. Alternatively, other known sources of energy forthermal dye transfer may be used, such as lasers as described in, forexample, GB No. 2,083,726A.

A thermal dye transfer assemblage comprises (a) a dye-donor element, and(b) a dye-receiving element as described above, the dye-receivingelement being in a superposed relationship with the dye-donor element sothat the dye layer of the donor element is in contact with the dyeimage-receiving layer of the receiving element.

When a three-color image is to be obtained, the above assemblage isformed on three occasions during the time when heat is applied by thethermal printing head. After the first dye is transferred, the elementsare peeled apart. A second dye-donor element (or another area of thedonor element with a different dye area) is then brought in registerwith the dye-receiving element and the process repeated. The third coloris obtained in the same manner.

In another embodiment, a thermal imaging system, described in, interalia, U.S. Pat. Nos. 4,771,032; 5,409,880; 5,410,335; 5,486,856; and5,537,140, and sold by Fuji Photo Film Co., Ltd. under the RegisteredTrademark “AUTOCHROME” which does not depend upon transfer of a dye,with or without a binder or carrier, from a donor to a receiving sheetmay be utilized with the present invention. The imaging element containsan imaging layer, which comprises plural heat-coloring elements, eachcomprising a diazo compound and a coupling component causingheat-coloring. Each of the diazo compounds in the heat-coloring elementsmay be decomposed by radiation having a respectively differentwavelength. The process uses a recording sheet having three separatesuperposed color-forming layers, each of which develops a differentcolor upon heating. The top color-forming layer develops color at alower temperature than the middle color-forming layer, which in turndevelops color at a lower temperature than the bottom color-forminglayer. Also, at least the top and middle color-forming layers may bedeactivated by actinic radiation of a specific wavelength (thewavelength for each color-forming layer being different, but bothtypically being in the near ultra-violet) so that after deactivation thecolor-forming layer will not generate color upon heating.

This recording sheet is imaged by first imagewise heating the sheet sothat color is developed in the top color-forming layer, the heatingbeing controlled so that no color is developed in either of the othertwo color-forming layers. The sheet is next passed beneath a radiationsource of a wavelength, which deactivates the top color-forming layer,but does not deactivate the middle color-forming layer. The sheet isthen again imagewise heated by the thermal head, but with the headproducing more heat than in the first pass, so that color is developedin the middle color-forming layer, and the sheet is passed beneath aradiation source of a wavelength, which deactivates the middlecolor-forming layer. Finally, the sheet is again imagewise heated by thethermal head, but with the head producing more heat than in the secondpass, so that color is developed in the bottom color-forming layer.

Briefly, in the system, heat-responsive microcapsules containing a dyeprecursor, diazonium salt are controlled by heat, whereby the contactbetween the inclusion and a developer and an organic base compoundhaving been prepared outside the microcapsules is controlled, or thatis, the reaction between them is controlled to thereby control the dyeformation resulting from the contact reaction. Next, the microcapsulesare exposed to UV rays so as to decompose the dye precursor. Thethus-decomposed dye precursor does not react with the coupler, andtherefore gives no color. The latter stage is for color image fixation.The heat-responsive microcapsules are meant to indicate microcapsules ofwhich the substance permeability through their walls varies under heat.For full-color imaging in the system, the heat-responsive microcapsulesthemselves and the diazonium salt to be therein are specificallydefined. The details of the system are in Printer Materials andChemicals (edited by Kyosuke Takahashi and Masahiro Irie, published byCMC, 1995).

The electrographic and electrophotographic processes and theirindividual steps have been well described in detail in many books andpublications. The processes incorporate the basic steps of creating anelectrostatic image, developing that image with charged, coloredparticles (toner), optionally transferring the resulting developed imageto a secondary substrate, and fixing the image to the substrate. Thereare numerous variations in these processes and basic steps; the use ofliquid toners in place of dry toners is simply one of those variations.

The first basic step, creation of an electrostatic image, may beaccomplished by a variety of methods. The electrophotographic process ofcopiers uses imagewise photodischarge, through analog or digitalexposure, of a uniformly charged photoconductor. The photoconductor maybe a single-use system, or it may be rechargeable and reimageable, likethose based on selenium or organic photoreceptors.

In an alternate electrographic process, electrostatic images are creatediono-graphically. The latent image is created on dielectric(charge-holding) medium, either paper or film. Voltage is applied toselected metal styli or writing nibs from an array of styli spacedacross the width of the medium, causing a dielectric breakdown of theair between the selected styli and the medium. Ions are created, whichform the latent image on the medium.

Electrostatic images, however generated, are developed with oppositelycharged toner particles. For development with liquid toners, the liquiddeveloper is brought into direct contact with the electrostatic image.Usually a flowing liquid is employed, to ensure that sufficient tonerparticles are available for development. The field created by theelectrostatic image causes the charged particles, suspended in anonconductive liquid, to move by electrophoresis. The charge of thelatent electrostatic image is thus neutralized by the oppositely chargedparticles. The theory and physics of electrophoretic development withliquid toners are well described in many books and publications.

If a reimageable photoreceptor or an electrographic master is used, thetoned image is transferred to paper (or other substrate). The paper ischarged electrostatically, with the polarity chosen to cause the tonerparticles to transfer to the paper. Finally, the toned image is fixed tothe paper. For self-fixing toners, residual liquid is removed from thepaper by air-drying or heating. Upon evaporation of the solvent thesetoners form a film bonded to the paper. For heat-fusible toners,thermoplastic polymers are used as part of the particle. Heating bothremoves residual liquid and fixes the toner to paper.

The dye receiving layer or DRL (dye receiving layer for thermalapplications) or the ink receiving layer (IRL for inkjet imaging) may beapplied by any known methods. Such as solvent coating, or melt extrusioncoating techniques. The DRL/IRL is coated over the TL (tie layer) at athickness ranging from 0.1–10 μm, preferably 0.5–5 μm. There are manyknown formulations, which may be useful as dye receiving layers. Theprimary requirement is that the DRL/IRL is compatible with the inks withwhich it will be imaged so as to yield the desirable color gamut anddensity. As the ink drops pass through the DRL/IRL, the dyes areretained or mordanted in the DRL/IRL, while the ink solvents pass freelythrough the DRL/IRL and are rapidly absorbed by the TL. Additionally,the DRL/IRL formulation is preferably coated from water, exhibitsadequate adhesion to the TL, and allows for easy control of the surfacegloss.

For example, Misuda et al. in U.S. Pat. Nos. 4,879,166; 5,264,275;5,104,730; 4,879,166, and Japanese patents 1,095,091; 2,276,671;2,276,670; 4,267,180; 5,024,335; and 5,016,517 discloses aqueous basedDRL/IRL formulations comprising mixtures of psuedo-bohemite and certainwater soluble resins. Light, in U.S. Pat. Nos. 4,903,040; 4,930,041;5,084,338; 5,126,194; 5,126,195; and 5,147,717 discloses aqueous-basedDRL/IRL formulations comprising mixtures of vinyl pyrrolidone polymersand certain water-dispersible and/or water-soluble polyesters, alongwith other polymers and addenda, also referred to herein as additives.Butters et al. in U.S. Pat. Nos. 4,857,386 and 5,102,717 discloseink-absorbent resin layers comprising mixtures of vinyl pyrrolidonepolymers and acrylic or methacrylic polymers. Sato et al. in U.S. Pat.No. 5,194,317 and Higuma et al. in U.S. Pat. No. 5,059,983 discloseaqueous-coatable DRL/IRL formulations based on poly (vinyl alcohol).Iqbal, in U.S. Pat. No. 5,208,092, discloses water-based DRL/IRLformulations comprising vinyl copolymers, which are subsequentlycross-linked. In addition to these examples, there may be other known orcontemplated DRL/IRL formulations, which are consistent with theaforementioned primary and secondary requirements of the DRL/IRL.

The preferred DRL is a 0.1–10 micrometers DRL which is coated as anaqueous dispersion of 5 parts alumoxane and 5 parts poly (vinylpyrrolidone). The DRL may also contain varying levels and sizes ofmatting agents for the purpose of controlling gloss, friction, and/orfinger print resistance, surfactants to enhance surface uniformity andto adjust the surface tension of the dried coating, mordanting agents,anti-oxidants, UV absorbing compounds, light stabilizers.

Although the dye or ink receiving elements as described above may besuccessfully used, it may be desirable to overcoat the DRL/IRL for thepurpose of enhancing the durability of the imaged element. Suchovercoats may be applied to the DRL/IRL either before or after theelement is imaged. For example, the DRL/IRL may be overcoated with anink-permeable layer through which inks freely pass. Layers of this typeare described in U.S. Pat. Nos. 4,686,118; 5,027,131; and 5,102,717.Alternatively, an overcoat may be added after the element is imaged. Anyof the known laminating films and equipment may be used for thispurpose. The inks used in the aforementioned imaging process are wellknown, and the ink formulations are often closely tied to the specificprocesses, that is, continuous, piezoelectric, or thermal. Therefore,depending on the specific ink process, the inks may contain widelydiffering amounts and combinations of solvents, colorants,preservatives, surfactants, humectants. Inks preferred for use incombination with the image recording elements are water-based, such asthose currently sold for use in the Hewlett-Packard Desk Writer 560Cprinter. However, it is intended that alternative embodiments of theimage-recording elements as described above, which may be formulated foruse with inks which are specific to a given ink-recording process or toa given commercial vendor.

The antistatic layer may be used in flat panel-type display products orother products having an electrically modulated imaging material on asupport. The support bears an electrically modulated imaging layer on atleast one surface. A suitable material may include electricallymodulated material disposed on a suitable support structure, such as onor between one or more electrodes. The term “electrically modulatedmaterial” as used herein is intended to include any suitablenon-volatile material. Suitable materials for the electrically modulatedmaterial are described in U.S. patent application Ser. No. 09/393,553and U.S. Provisional Patent Application Ser. No. 60/099,888, thecontents of both applications are herein incorporated by reference.

The electrically modulated material may also be a printable, conductiveink having an arrangement of particles or microscopic containers ormicrocapsules. Each microcapsule contains an electrophoretic compositionof a fluid, such as a dielectric or emulsion fluid, and a suspension ofcolored or charged particles or colloidal material. The diameter of themicrocapsules typically ranges from about 30 to about 300 microns.According to one practice, the particles visually contrast with thedielectric fluid. According to another example, the electricallymodulated material may include rotatable balls that can rotate to exposea different colored surface area, and which can migrate between aforward viewing position and/or a rear non-viewing position, such asgyricon. Specifically, gyricon is a material comprised of twistingrotating elements contained in liquid-filled spherical cavities andembedded in an elastomer medium. The rotating elements may be made toexhibit changes in optical properties by the imposition of an externalelectric field. Upon application of an electric field of a givenpolarity, one segment of a rotating element rotates toward, and isvisible by an observer of the display. Application of an electric fieldof opposite polarity, causes the element to rotate and expose a second,different segment to the observer. A gyricon display maintains a givenconfiguration until an electric field is actively applied to the displayassembly. Gyricon particles typically have a diameter of about 100microns. Gyricon materials are disclosed in U.S. Pat. No. 6,147,791,U.S. Pat. No. 4,126,854 and U.S. Pat. No. 6,055,091, the contents ofwhich are herein incorporated by reference.

According to one practice, the microcapsules may be filled withelectrically charged white particles in a black or colored dye. Examplesof electrically modulated material and methods of fabricating assembliescapable of controlling or effecting the orientation of the ink suitablefor use with the present invention are set forth in International PatentApplication Publication Number WO 98/41899, International PatentApplication Publication Number WO 98/19208, International PatentApplication Publication Number WO 98/03896, and International PatentApplication Publication Number WO 98/41898, the contents of which areherein incorporated by reference.

The electrically modulated material may also include material disclosedin U.S. Pat. No. 6,025,896, the contents of which are incorporatedherein by reference. This material comprises charged particles in aliquid dispersion medium encapsulated in a large number ofmicrocapsules. The charged particles can have different types of colorand charge polarity. For example white positively charged particles canbe employed along with black negatively charged particles. The describedmicrocapsules are disposed between a pair of electrodes, such that adesired image is formed and displayed by the material by varying thedispersion state of the charged particles. The dispersion state of thecharged particles is varied through a controlled electric field appliedto the electrically modulated material material. According to apreferred embodiment, the particle diameters of the microcapsules arebetween about 5 microns and about 200 microns, and the particlediameters of the charged particles are between about one-thousandth andone-fifth the size of the particle diameters of the microcapsules.

Further, the electrically modulated material may include athermo-chromic material. A thermo-chromic material is capable ofchanging its state alternately between transparent and opaque upon theapplication of heat. In this manner, a thermo-chromic imaging materialdevelops images through the application of heat at specific pixellocations in order to form an image. The thermo-chromic imaging materialretains a particular image until heat is again applied to the material.Since the rewritable material is transparent, UV fluorescent printings,designs and patterns underneath can be seen through.

The electrically modulated material may also include surface stabilizedferrroelectric liquid crystals (SSFLC). Surface stabilized ferroelectricliquid crystals confining ferroelectric liquid crystal material betweenclosely-spaced glass plates to suppress the natural helix configurationof the crystals. The cells switch rapidly between two opticallydistinct, stable states simply by alternating the sign of an appliedelectric field.

Magnetic particles suspended in an emulsion comprise an additionalimaging material suitable for use with the present invention.Application of a magnetic force alters pixels formed with the magneticparticles in order to create, update or change human and/or machinereadable indicia. Those skilled in the art will recognize that a varietyof bi-stable non-volatile imaging materials are available and may beimplemented in the present invention.

The electrically modulated material may also be configured as a singlecolor, such as black, white or clear, and may be fluorescent,iridescent, bioluminescent, incandescent, ultraviolet, infrared, or mayinclude a wavelength specific radiation absorbing or emitting material.There may be multiple layers of electrically modulated material.Different layers or regions of the electrically modulated materialdisplay material may have different properties or colors. Moreover, thecharacteristics of the various layers may be different from each other.For example, one layer can be used to view or display information in thevisible light range, while a second layer responds to or emitsultraviolet light. The non-visible layers may alternatively beconstructed of non-electrically modulated material based materials thathave the previously listed radiation absorbing or emittingcharacteristics. The electrically modulated material employed inconnection with the present invention preferably has the characteristicthat it does not require power to maintain display of indicia.

The preferred electrically modulated imaging layer comprises a lightmodulating material, preferably, a liquid crystalline material. Liquidcrystals can be nematic (N), chiral nematic (N*), or smectic, dependingupon the arrangement of the molecules in the mesophase. Chiral nematicliquid crystal (N*LC) displays are typically reflective, that is, nobacklight is needed, and can function without the use of polarizingfilms or a color filter.

Chiral nematic liquid crystal, also called cholesteric liquid crystal,refers to the type of liquid crystal having finer pitch than that oftwisted nematic and super-twisted nematic used in commonly encounteredLC devices. Chiral nematic liquid crystals are so named because suchliquid crystal formulations are commonly obtained by adding chiralagents to host nematic liquid crystals. Chiral nematic liquid crystalsmay be used to produce bi-stable or multi-stable displays. These deviceshave significantly reduced power consumption due to their non-volatile“memory” characteristic. Since such displays do not require a continuousdriving circuit to maintain an image, they consume significantly reducedpower. Chiral nematic displays are bistable in the absence of a field;the two stable textures are the reflective planar texture and the weaklyscattering focal conic texture. In the planar texture, the helical axesof the chiral nematic liquid crystal molecules are substantiallyperpendicular to the substrate upon which the liquid crystal isdisposed. In the focal conic state the helical axes of the liquidcrystal molecules are generally randomly oriented. Adjusting theconcentration of chiral dopants in the chiral nematic material modulatesthe pitch length of the mesophase and, thus, the wavelength of radiationreflected. Chiral nematic materials that reflect infrared radiation andultraviolet have been used for purposes of scientific study. Commercialdisplays are most often fabricated from chiral nematic materials thatreflect visible light. Some known LCD devices include chemically-etched,transparent, conductive layers overlying a glass substrate as describedin U.S. Pat. No. 5,667,853, incorporated herein by reference.

In one embodiment, a chiral-nematic liquid crystal composition may bedispersed in a continuous matrix. Such materials are referred to as“polymer-dispersed liquid crystal” materials or “PDLC” materials. Suchmaterials can be made by a variety of methods. For example, Doane et al.(Applied Physics Letters, 48, 269 (1986)) disclose a PDLC comprisingapproximately 0.4 mm droplets of nematic liquid crystal 5CB in a polymerbinder. A phase separation method is used for preparing the PDLC. Asolution containing monomer and liquid crystal is filled in a displaycell and the material is then polymerized. Upon polymerization theliquid crystal becomes immiscible and nucleates to form droplets. Westet al. (Applied Physics Letters 63, 1471 (1993)) disclose a PDLCcomprising a chiral nematic mixture in a polymer binder. Once again aphase separation method is used for preparing the PDLC. The liquidcrystal material and polymer (a hydroxy functionalizedpolymethylmethacrylate) along with a cross-linker for the polymer aredissolved in a common organic solvent toluene and coated on an indiumtin oxide (ITO) substrate. A dispersion of the liquid-crystal materialin the polymer binder is formed upon evaporation of toluene at hightemperature. The phase separation methods of Doane et al. and West etal. require the use of organic solvents that may be objectionable incertain manufacturing environments.

In one embodiment, the liquid crystal may be applied as a substantialmonolayer. The term “substantial monolayer” is defined by the Applicantsto mean that, in a direction perpendicular to the plane of the display,there is no more than a single layer of domains sandwiched between theelectrodes at most points of the display (or the imaging layer),preferably at 75 percent or more of the points (or area) of the display,most preferably at 90 percent or more of the points (or area) of thedisplay. In other words, at most, only a minor portion (preferably lessthan 10 percent) of the points (or area) of the display has more than asingle domain (two or more domains) between the electrodes in adirection perpendicular to the plane of the display, compared to theamount of points (or area) of the display at which there is only asingle domain between the electrodes.

The amount of material needed for a monolayer can be accuratelydetermined by calculation based on individual domain size, assuming afully closed packed arrangement of domains. (In practice, there may beimperfections in which gaps occur and some unevenness due to overlappingdroplets or domains.) On this basis, the calculated amount is preferablyless than about 150 percent of the amount needed for monolayer domaincoverage, preferably not more than about 125 percent of the amountneeded for a monolayer domain coverage, more preferably not more than110 percent of the amount needed for a monolayer of domains.Furthermore, improved viewing angle and broadband features may beobtained by appropriate choice of differently doped domains based on thegeometry of the coated droplet and the Bragg reflection condition.

In a preferred embodiment of the invention, the display device ordisplay sheet has simply a single imaging layer of liquid crystalmaterial along a line perpendicular to the face of the display,preferably a single layer coated on a flexible substrate. Such astructure, as compared to vertically stacked imaging layers each betweenopposing substrates, is especially advantageous for monochrome shelflabels and the like. Structures having stacked imaging layers, however,are optional for providing additional advantages in some cases, such asmulti-color or full-color (eg RGB) displays.

Preferably, the domains are flattened spheres and have on average athickness substantially less than their length, preferably at least 50%less. More preferably, the domains on average have a thickness (depth)to length ratio of 1:2 to 1:6. The flattening of the domains can beachieved by proper formulation and sufficiently rapid drying of thecoating. The domains preferably have an average diameter of 2 to 30microns. The imaging layer preferably has a thickness of 10 to 150microns when first coated and 2 to 20 microns when dried.

The flattened domains of liquid crystal material can be defined ashaving a major axis and a minor axis. In a preferred embodiment of adisplay or display sheet, the major axis is larger in size than the cell(or imaging layer) thickness for a majority of the domains. Such adimensional relationship is shown in U.S. Pat. No. 6,061,107, herebyincorporated by reference in its entirety.

Modern chiral nematic liquid crystal materials usually include at leastone nematic host combined with a chiral dopant. In general, the nematicliquid crystal phase is composed of one or more mesogenic componentscombined to provide useful composite properties. Many such materials areavailable commercially. The nematic component of the chiral nematicliquid crystal mixture may be comprised of any suitable nematic liquidcrystal mixture or composition having appropriate liquid crystalcharacteristics. The nematic liquid crystal phases typically consist of2 to 20, preferably 2 to 15 components. The above list of materials isnot intended to be exhaustive or limiting. The lists disclose a varietyof representative materials suitable for use or mixtures, which comprisethe active element in electro-optic liquid crystal compositions.

Suitable chiral nematic liquid crystal compositions preferably have apositive dielectric anisotropy and include chiral material in an amounteffective to form focal conic and twisted planar textures. Chiralnematic liquid crystal materials are preferred because of theirexcellent reflective characteristics, bi-stability and gray scalememory. The chiral nematic liquid crystal is typically a mixture ofnematic liquid crystal and chiral material in an amount sufficient toproduce the desired pitch length. Suitable commercial nematic liquidcrystals include, for example, E7, E44, E48, E31, E80, BL087, BL101,ZLI-3308, ZLI-3273, ZLI-5048-000, ZLI-5049-100, ZLI-5100-100,ZLI-5800-000, MLC-6041-100.TL202, TL203, TL204 and TL205 manufactured byE. Merck (Darmstadt, Germany). Although nematic liquid crystals havingpositive dielectric anisotropy, and especially cyanobiphenyls, arepreferred, virtually any nematic liquid crystal known in the art,including those having negative dielectric anisotropy should be suitablefor use in the invention. Other nematic materials may also be suitablefor use in the present invention as would be appreciated by thoseskilled in the art.

The chiral dopant added to the nematic mixture to induce the helicaltwisting of the mesophase, thereby allowing reflection of visible light,can be of any useful structural class. The choice of dopant depends uponseveral characteristics including among others its chemicalcompatibility with the nematic host, helical twisting power, temperaturesensitivity, and light fastness. Many chiral dopant classes are known inthe art: e.g., G. Gottarelli and G. Spada, Mol. Cryst. Liq. Crys., 123,377 (1985); G. Spada and G. Proni, Enantiomer, 3, 301 (1998), U.S. Pat.No. 6,217,792; U.S. Pat. No. 6,099,751; and U.S. patent application Ser.No. 10/651,692, hereby incorporated by reference.

Chiral nematic liquid crystal materials and cells, as well as polymerstabilized chiral nematic liquid crystals and cells, are well known inthe art and described in, for example, co-pending application Ser. No.07/969,093 filed Oct. 30, 1992; Ser. No. 08/057,662 filed May 4, 1993;Yang et al., Appl. Phys. Lett. 60(25) pp 3102–04 (1992); Yang et al., J.Appl. Phys. 76(2) pp 1331 (1994); published International PatentApplication No. PCT/US92/09367; and published International PatentApplication No. PCT/US92/03504, all of which are incorporated herein byreference.

The liquid crystalline droplets or domains may be formed by any method,known to those of skill in the art, which will allow control of thedomain size. Liquid crystal domains are preferably made using a limitedcoalescence methodology, as disclosed in U.S. Pat. Nos. 6,556,262 and6,423,368, incorporated herein by reference. Limited coalescence isdefined as dispersing a light-modulating material below a given size,and using coalescent limiting material to limit the size of theresulting domains. Such materials are characterized as having a ratio ofmaximum to minimum domain size of less than 2:1. By use of the term“uniform domains”, it is meant that domains are formed having a domainsize variation of less than 2:1. Limited domain materials have improvedoptical properties.

An immiscible, field responsive light-modulating material along with aquantity of colloidal particles is dispersed in an aqueous system andblended to form a dispersion of field-responsive, light-modulatingmaterial below a coalescence size. When the dispersion, also referred toherein as an emulsion, is dried, a coated material is produced which hasa set of uniform domains having a plurality of electrically responsiveoptical states. The colloidal solid particle, functioning as anemulsifier, limits domain growth from a highly dispersed state.Uniformly sized liquid crystal domains are created and machine coated tomanufacture light-modulating, electrically responsive sheets withimproved optical efficiency.

Specifically, a liquid crystal material may be dispersed an aqueous bathcontaining a water-soluble binder material such as de-ionized gelatin,polyvinyl alcohol (PVA) or polyethylene oxide (PEO). Such compounds aremachine coatable on equipment associated with photographic films.Preferably, the binder has a low ionic content, as the presence of ionsin such a binder hinders the development of an electrical field acrossthe dispersed liquid crystal material. Additionally, ions in the bindercan migrate in the presence of an electrical field, chemically damagingthe light-modulating layer. The liquid crystal/gelatin emulsion iscoated to a thickness of between 5 and 30 microns to optimize opticalproperties of light modulating layer. The coating thickness, size of theliquid crystal domains, and concentration of the domains of liquidcrystal materials are designed for optimum optical properties.

In an exemplary embodiment, a liquid crystalline material is homogenizedin the presence of finely divided silica, a coalescence limitingmaterial, (LUDOX® from duPont Corporation). A promoter material, such asa copolymer of adipic acid and 2-(methylamino) ethanol, is added to theaqueous bath to drive the colloidal particles to the liquid-liquidinterface. The liquid crystal material is dispersed using ultrasound tocreate liquid crystal domains below 1 micron in size. When theultrasound energy was removed, the liquid crystal material coalescedinto domains of uniform size. The ratio of smallest to largest domainsize varied by approximately 1:2. By varying the amount of silica andcopolymer relative to the liquid crystalline material, uniform domainsize emulsions of average diameter (by microscopy) approximately 1, 3,and, 8 micron were produced. These emulsions were diluted into gelatinsolution for subsequent coating.

Domains of a limited coalescent material maintain their uniform sizeafter the addition of the surfactant and after being machine coated.There were few, if any, parasitic domains having undesirableelectro-optical properties within the dried coatings produced by thelimited coalescence method. Coatings made using limited coalescencehaving a domain size of about 2 microns may have the greatesttranslucence. For constant material concentrations and coatingthickness, limited coalescent materials having a domain size of about 2microns in size are significantly more translucent than any sizeddomains formed using conventional dispersion.

Sheets made by the limited coalescence process have curves similar tothose of conventionally dispersed materials. However, with 8 to 10micron domains, the material may demonstrate reduced scattering due tothe elimination of parasitic domains. Conventionally dispersedcholesteric materials contain parasitic domains, which reflect light inwavelengths outside the wavelengths reflected by the cholestericmaterial. Limited coalescent dispersions have reduced reflection inother wavelengths due to the elimination of parasitic domains. Theincreased purity of color is important in the development of full colordisplays requiring well-separated color channels to create a full-colorimage. Limited coalescent cholesteric materials provide purer lightreflectance than cholesteric liquid crystal material dispersed byconventional methods. Such materials may be produced using conventionalphotographic coating machinery.

In order to provide suitable formulations for applying a layercontaining the liquid crystal domains, the dispersions are combined witha hydrophilic colloid, gelatin being the preferred material. Surfactantsmay be included with the lubricant dispersion prior to the addition ofgelatin in order to prevent the removal of the particulate suspensionstabilizing agent from the droplets. This aids in preventing furthercoalescence of the droplets.

As for the suspension stabilizing agents that surround and serve toprevent the coalescence of the droplets, any suitable colloidalstabilizing agent known in the art of forming polymeric particles by theaddition reaction of ethylenically unsaturated monomers by the limitedcoalescence technique can be employed, such as, for example, inorganicmaterials such as, metal salt or hydroxides or oxides or clays, organicmaterials such as starches, sulfonated crosslinked organic homopolymersand resinous polymers as described, for example, in U.S. Pat. No.2,932,629; silica as described in U.S. Pat. No. 4,833,060; copolymerssuch as copoly(styrene-2-hydroxyethyl methacrylate-methacrylicacid-ethylene glycol dimethacrylate) as described in U.S. Pat. No.4,965,131, all of which are incorporated herein by reference. Silica isthe preferred suspension stabilizing agent.

Suitable promoters to drive the suspension stabilizing agent to theinterface of the droplets and the aqueous phase include sulfonatedpolystyrenes, alginates, carboxymethyl cellulose, tetramethyl ammoniumhydroxide or chloride, triethylphenyl ammonium hydroxide, triethylphenylammonium hydroxide, triethylphenyl ammonium chloride,diethylaminoethylmethacrylate, water-soluble complex resinous aminecondensation products, such as the water soluble condensation product ofdiethanol amine and adipic acid, such as poly(adipicacid-co-methylaminoethanol), water soluble condensation products ofethylene oxide, urea, and formaldehyde and polyethyleneimine; gelatin,glue, casein, albumin, gluten, and methoxycellulose. The preferredpromoter is triethylphenyl ammonium chloride.

In order to prevent the hydrophilic colloid from removing the suspensionstabilizing agent from the surface of the droplets, suitable anionicsurfactants may be included in the mixing step to prepare the coatingcomposition such as polyisopropyl naphthalene-sodium sulfonate, sodiumdodecyl sulfate, sodium dodecyl benzene sulfonate, as well as thoseanionic surfactants set forth in U.S. Pat. No. 5,326,687 and in SectionXI of Research Disclosure 308119, December 1989, entitled “PhotographicSilver Halide Emulsions, Preparations, Addenda, Processing, andSystems”, both of which are incorporated herein by reference. Aromaticsulfonates are more preferred and polyisopropyl naphthalene sulfonate ismost preferred.

Suitable hydrophilic binders include both naturally occurring substancessuch as proteins, protein derivatives, cellulose derivatives (e.g.cellulose esters), gelatins and gelatin derivatives, polysaccaharides,casein, and the like, and synthetic water permeable colloids such aspoly(vinyl lactams), acrylamide polymers, poly(vinyl alcohol) and itsderivatives, hydrolyzed polyvinyl acetates, polymers of alkyl andsulfoalkyl acrylates and methacrylates, polyamides, polyvinyl pyridine,acrylic acid polymers, maleic anhydride copolymers, polyalkylene oxide,methacrylamide copolymers, polyvinyl oxazolidinones, maleic acidcopolymers, vinyl amine copolymers, methacrylic acid copolymers,acryloyloxyalkyl acrylate and methacrylates, vinyl imidazole copolymers,vinyl sulfide copolymers, and homopolymer or copolymers containingstyrene sulfonic acid. Gelatin is preferred.

Gelatin, containing hardener, may optionally be used in the presentinvention. In the context of this invention, hardeners are defined asany additive, which causes chemical crosslinking in gelatin or gelatinderivatives. Many conventional hardeners are known to crosslink gelatin.Gelatin crosslinking agents (i.e., the hardener) are included in anamount of at least about 0.01 wt. % and preferably from about 0.1 toabout 10 wt. % based on the weight of the solid dried gelatin materialused (by dried gelatin is meant substantially dry gelatin at ambientconditions as for example obtained from Eastman Gel Co., as compared toswollen gelatin), and more preferably in the amount of from about 1 toabout 5 percent by weight. More than one gelatin crosslinking agent canbe used if desired. Suitable hardeners may include inorganic, organichardeners, such as aldehyde hardeners and olefinic hardeners. Inorganichardeners include compounds such as aluminum salts, especially thesulfate, potassium and ammonium alums, ammonium zirconium carbonate,chromium salts such as chromium sulfate and chromium alum, and salts oftitanium dioxide, and zirconium dioxide. Representative organichardeners or gelatin crosslinking agents may include aldehyde andrelated compounds, pyridiniums, olefins, carbodiimides, and epoxides.Thus, suitable aldehyde hardeners include formaldehyde and compoundsthat contain two or more aldehyde functional groups such as glyoxal,gluteraldehyde and the like. Other preferred hardeners include compoundsthat contain blocked aldehyde functional groups such as aldehydes of thetype tetrahydro-4-hydroxy-5-methyl-2(1H)-pyrimidinone polymers (SequaSUNREZâ 700), polymers of the type having a glyoxal polyol reactionproduct consisting of 1 anhydroglucose unit: 2 glyoxal units (SEQUAREZâ755 obtained from Sequa Chemicals, Inc.), DME-Melamine non-formaldehyderesins such as Sequa CPD3046-76 obtained from Sequa Chemicals Inc., and2,3-dihydroxy-1,4-dioxane (DHD). Thus, hardeners that contain activeolefinic functional groups include, for example,bis-(vinylsulfonyl)-methane (BVSM), bis-(vinylsulfonyl-methyl) ether(BVSME), 1,3,5-triacryloylhexahydro-s-triazine, and the like. In thecontext of the present invention, active olefinic compounds are definedas compounds having two or more olefinic bonds, especially unsubstitutedvinyl groups, activated by adjacent electron withdrawing groups (TheTheory of the Photographic Process, 4th Edition, T. H. James, 1977,Macmillan Publishing Co., page 82). Other examples of hardening agentscan be found in standard references such as The Theory of thePhotographic Process, T. H. James, Macmillan Publishing Co., Inc. (NewYork 1977) or in Research Disclosure, September 1996, Vol. 389, Part IIB(Hardeners) or in Research Disclosure, September 1994, Vol. 365, Item36544, Part IIB (Hardeners). Research Disclosure is published by KennethMason Publications, Ltd., Dudley House, 12 North St., Emsworth,Hampshire P010 7DQ, England. Olefinic hardeners are most preferred, asdisclosed in U.S. Pat. Nos. 3,689,274, 2,994,611, 3,642,486, 3,490,911,3,635,718, 3,640,720, 2,992,109, 3,232,763, and 3,360,372.

Among hardeners of the active olefin type, a preferred class ofhardeners particularly are compounds comprising two or more vinylsulfonyl groups. These compounds are hereinafter referred to as “vinylsulfones.” Compounds of this type are described in numerous patentsincluding, for example, U.S. Pat. Nos. 3,490,911, 3,642,486, 3,841,872and 4,171,976. Vinyl sulfone hardeners are believed to be effective ashardeners as a result of their ability to crosslink polymers making upthe colloid.

As used herein, the phase a “liquid crystal display” (LCD) is a type offlat panel display used in various electronic devices. At a minimum, anLCD comprises a substrate, at least one conductive layer and a liquidcrystal layer. LCDs may also comprise two sheets of polarizing materialwith a liquid crystal solution between the polarizing sheets. The sheetsof polarizing material may comprise a substrate of glass or transparentplastic. The LCD may also include functional layers. In one embodimentof an LCD, a transparent, multilayer flexible support is coated with afirst conductive layer, which may be patterned, onto which is coated thelight-modulating liquid crystal layer. A second conductive layer isapplied and overcoated with a dielectric layer to which dielectricconductive row contacts are attached, including vias that permitinterconnection between conductive layers and the dielectric conductiverow contacts. An optional nanopigmented functional layer may be appliedbetween the liquid crystal layer and the second conductive layer.

The liquid crystal (LC) is used as an optical switch. The substrates areusually manufactured with transparent, conductive electrodes, in whichelectrical “driving” signals are coupled. The driving signals induce anelectric field which can cause a phase change or state change in the LCmaterial, the LC exhibiting different light-reflecting characteristicsaccording to its phase and/or state.

There are alternative display technologies to LCDs that can be used, forexample, in flat panel displays. A notable example is organic or polymerlight-emitting devices (OLEDs) or (PLEDs), which are comprised ofseveral layers in which one of the layers is comprised of an organicmaterial that can be made to electroluminesce by applying a voltageacross the device. An OLED device is typically a laminate formed in asubstrate such as glass or a plastic polymer. A light-emitting layer ofa luminescent organic solid, as well as adjacent semiconductor layers,are sandwiched between an anode and a cathode. The semiconductor layerscan be whole-injecting and electron-injecting layers. PLEDs can beconsidered a subspecies of OLEDs in which the luminescent organicmaterial is a polymer. The light-emitting layers may be selected fromany of a multitude of light-emitting organic solids, e.g., polymers thatare suitably fluorescent or chemiluminescent organic compounds. Suchcompounds and polymers include metal ion salts of 8-hydroxyquinolate,trivalent metal quinolate complexes, trivalent metal bridged quinolatecomplexes, Schiff-based divalent metal complexes, tin (IV) metalcomplexes, metal acetylacetonate complexes, metal bidenate ligandcomplexes incorporating organic ligands, such as 2-picolylketones,2-quinaldylketones, or 2-(o-phenoxy) pyridine ketones, bisphosphonates,divalent metal maleonitriledithiolate complexes, molecular chargetransfer complexes, rare earth mixed chelates, (5-hydroxy) quinoxalinemetal complexes, aluminum tris-quinolates, and polymers such aspoly(p-phenylenevinylene), poly(dialkoxyphenylenevinylene),poly(thiophene), poly(fluorene), poly(phenylene), poly(phenylacetylene),poly(aniline), poly(3-alkylthiophene), poly(3-octylthiophene), andpoly(N-vinylcarbazole). When a potential difference is applied acrossthe cathode and anode, electrons from the electron-injecting layer andholes from the hole-injecting layer are injected into the light-emittinglayer; they recombine, emitting light. OLEDs and PLEDs are described inthe following United States patents, all of which are incorporatedherein by this reference: U.S. Pat. No. 5,707,745 to Forrest et al.,U.S. Pat. No. 5,721,160 to Forrest et al., U.S. Pat. No. 5,757,026 toForrest et al., U.S. Pat. No. 5,834,893 to Bulovic et al., U.S. Pat. No.5,861,219 to Thompson et al., U.S. Pat. No. 5,904,916 to Tang et al.,U.S. Pat. No. 5,986,401 to Thompson et al., U.S. Pat. No. 5,998,803 toForrest et al., U.S. Pat. No. 6,013,538 to Burrows et al., U.S. Pat. No.6,046,543 to Bulovic et al., U.S. Pat. No. 6,048,573 to Tang et al.,U.S. Pat. No. 6,048,630 to Burrows et al., U.S. Pat. No. 6,066,357 toTang et al., U.S. Pat. No. 6,125,226 to Forrest et al., U.S. Pat. No.6,137,223 to Hung et al., U.S. Pat. No. 6,242,115 to Thompson et al.,and U.S. Pat. No. 6,274,980 to Burrows et al.

In a typical matrix-address light-emitting display device, numerouslight-emitting devices are formed on a single substrate and arranged ingroups in a regular grid pattern, usually to permit the formation offorming an image or text. Activation may be by rows and columns, or inan active matrix with individual cathode and anode paths. OLEDs areoften manufactured by first depositing a transparent electrode on thesubstrate, and patterning the same into electrode portions. The organiclayer(s) is then deposited over the transparent electrode. A metallicelectrode can be formed over the electrode layers. For example, in U.S.Pat. No. 5,703,436 to Forrest et al., incorporated herein by reference,transparent indium tin oxide (ITO) is used as the whole-injectingelectrode, and a Mg——Ag—-ITO electrode layer is used for electroninjection.

Preferably, the substrate for the display is a flexible plasticsubstrate, which can be any flexible self-supporting plastic film thatsupports the thin conductive metallic film. “Plastic” means a highpolymer, usually made from polymeric synthetic resins, which may becombined with other ingredients, such as curatives, fillers, reinforcingagents, colorants, and plasticizers. Plastic includes thermoplasticmaterials and thermosetting materials.

The flexible plastic film must have sufficient thickness and mechanicalintegrity so as to be self-supporting, yet should not be so thick as tobe rigid. Typically, the flexible plastic substrate is the thickestlayer of the composite film in thickness. Consequently, the substratedetermines to a large extent the mechanical and thermal stability of thefully structured composite film.

Another significant characteristic of the flexible plastic substratematerial is its glass transition temperature (Tg). Tg is defined as theglass transition temperature at which plastic material will change fromthe glassy state to the rubbery state. It may comprise a range beforethe material may actually flow. Suitable materials for the flexibleplastic substrate include thermoplastics of a relatively low glasstransition temperature, for example up to 150° C., as well as materialsof a higher glass transition temperature, for example, above 150° C. Thechoice of material for the flexible plastic substrate would depend onfactors such as manufacturing process conditions, such as depositiontemperature, and annealing temperature, as well as post-manufacturingconditions such as in a process line of a displays manufacturer. Certainof the plastic substrates discussed below can withstand higherprocessing temperatures of up to at least about 200° C., some up to3000–350° C., without damage.

Typically, the flexible plastic substrate is polyethylene terephthalate(PET), polyethylene naphthalate (PEN), polyethersulfone (PES),polycarbonate (PC), polysulfone, a phenolic resin, an epoxy resin,polyester, polyimide, polyamide, polyetherester, polyetheramide,acetate, for example, cellulose acetate, aliphatic polyurethanes,polyacrylonitrile, polytetrafluoroethylenes, polyvinylidene fluorides,poly(methyl α-methacrylates), an aliphatic or cyclic polyolefin,polyarylate (PAR), polyetherimide (PEI), polyethersulphone (PES),polyimide (PI), Teflon poly(perfluoro-alboxy) fluoropolymer (PFA),poly(ether ether ketone) (PEEK), poly(ether ketone) (PEK), poly(ethylenetetrafluoroethylene)fluoropolymer (PETFE), and poly(methyl methacrylate)and various acrylate/methacrylate copolymers (PMMA). Aliphaticpolyolefins may include high density polyethylene (HDPE), low densitypolyethylene (LDPE), and polypropylene, including oriented polypropylene(OPP). Polyolefins and cyclic polyolefins may be included. A preferredflexible plastic substrate is a cyclic polyolefin or a polyester.Various cyclic polyolefins are suitable for the flexible plasticsubstrate. Examples include Arton® made by Japan Synthetic Rubber Co.,Tokyo, Japan; Zeanor T made by Zeon Chemicals L. P., Tokyo Japan; andTopas® made by Celanese A. G., Kronberg Germany. Arton is apoly(bis(cyclopentadiene)) condensate that is a film of a polymer. Apreferred polyester is an aromatic polyester such as Arylite. Althoughvarious examples of plastic substrates are set forth above, it should beappreciated that the substrate can also be formed from other materialssuch as glass and quartz.

The flexible plastic substrate can be reinforced with a hard coating.Typically, the hard coating is an acrylic coating. Such a hard coatingtypically has a thickness of from 1 to 15 microns, preferably from 2 to4 microns and can be provided by free radical polymerization, initiatedeither thermally or by ultraviolet radiation, of an appropriatepolymerizable material. Depending on the substrate, different hardcoatings can be used. When the substrate is polyester or Arton, aparticularly preferred hard coating is the coating known as “Lintec.”Lintec contains UV-cured polyester acrylate and colloidal silica. Whendeposited on Arton, it has a surface composition of 35 atom % C, 45 atom% 0, and 20 atom % Si, excluding hydrogen. Another particularlypreferred hard coating is the acrylic coating sold under the trademark“Terrapin” by Tekra Corporation, New Berlin, Wis.

In one embodiment, a sheet supports a conventional polymer dispersedlight-modulating material. The sheet includes a substrate. The substratemay be made of a polymeric material, such as Kodak Estar film baseformed of polyester plastic, and have a thickness of between 20 and 200microns. For example, the substrate may be an 80 micron thick sheet oftransparent polyester. Other polymers, such as transparentpolycarbonate, can also be used. Alternatively, the substrate 15 may bethin, transparent glass.

The LCD contains at least one conductive layer, which typically iscomprised of a primary metal oxide. This conductive layer may compriseother metal oxides such as indium oxide, titanium dioxide, cadmiumoxide, gallium indium oxide, niobium pentoxide and tin dioxide. See,Int. Publ. No. WO 99/36261 by Polaroid Corporation. In addition to theprimary oxide such as ITO, the at least one conductive layer can alsocomprise a secondary metal oxide such as an oxide of cerium, titanium,zirconium, hafnium and/or tantalum. See, U.S. Pat. No. 5,667,853 toFukuyoshi et al. (Toppan Printing Co.) Other transparent conductiveoxides include, but are not limited to ZnO2, Zn2SnO4, Cd2SnO4, Zn2In2O5,MgIn2O4, Ga2O3—In2O3, or TaO3. The conductive layer may be formed, forexample, by a low temperature sputtering technique or by a directcurrent sputtering technique, such as DC-sputtering or RF-DC sputtering,depending upon the material or materials of the underlying layer. Theconductive layer may be a transparent, electrically conductive layer oftin-oxide or indium-tin-oxide (ITO), or polythiophene, with ITO beingthe preferred material. Typically, the conductive layer is sputteredonto the substrate to a resistance of less than 250 ohms per square.Alternatively, conductive layer may be an opaque electrical conductorformed of metal such as copper, aluminum or nickel. If the conductivelayer is an opaque metal, the metal can be a metal oxide to create alight absorbing conductive layer.

Indium tin oxide (ITO) is the preferred conductive material, as it is acost effective conductor with good environmental stability, up to 90%transmission, and down to 20 ohms per square resistivity. An exemplarypreferred ITO layer has a % T greater than or equal to 80% in thevisible region of light, that is, from greater than 400 nm to 700 nm, sothat the film will be useful for display applications. In a preferredembodiment, the conductive layer comprises a layer of low temperatureITO which is polycrystalline. The ITO layer is preferably 10–120 nm inthickness, or 50–100 nm thick to achieve a resistivity of 20–60ohms/square on plastic. An exemplary preferred ITO layer is 60–80 nmthick. The electrically conductive layers typically have a surfaceconductivity of less than 10⁴ ohms/sq, a sufficient conductivity toinduce an electric field strong enough to change the optical state of alight modulating material.

The conductive layer is preferably patterned. The conductive layer ispreferably patterned into a plurality of electrodes. The patternedelectrodes may be used to form a LCD device. In another embodiment, twoconductive substrates are positioned facing each other and cholestericliquid crystals are positioned therebetween to form a device. Thepatterned ITO conductive layer may have a variety of dimensions.Exemplary dimensions may include line widths of 10 microns, distancesbetween lines, that is, electrode widths, of 200 microns, depth of cut,that is, thickness of ITO conductor, of 100 nanometers. ITO thicknesseson the order of 60, 70, and greater than 100 nanometers are alsopossible.

The display may also contain a second conductive layer applied to thesurface of the light-modulating layer. The second conductive layerdesirably has sufficient conductivity to carry a field across thelight-modulating layer. The second conductive layer may be formed in avacuum environment using materials such as aluminum, tin, silver,platinum, carbon, tungsten, molybdenum, or indium. Oxides of thesemetals can be used to darken patternable conductive layers. The metalmaterial can be excited by energy from resistance heating, cathodic arc,electron beam, sputtering or magnetron excitation. The second conductivelayer may comprise coatings of tin-oxide or indium-tin oxide, resultingin the layer being transparent. Alternatively, second conductive layermay be printed conductive ink.

For higher conductivities, the second conductive layer may comprise asilver-based layer which contains silver only or silver containing adifferent element such as aluminum (Al), copper (Cu), nickel (Ni),cadmium (Cd), gold (Au), zinc (Zn), magnesium (Mg), tin (Sn), indium(In), tantalum (Ta), titanium (Ti), zirconium (Zr), cerium (Ce), silicon(Si), lead (Pb) or palladium (Pd). In a preferred embodiment, theconductive layer comprises at least one of gold, silver and agold/silver alloy, for example, a layer of silver coated on one or bothsides with a thinner layer of gold. See, Int. Publ. No. WO 99/36261 byPolaroid Corporation. In another embodiment, the conductive layer maycomprise a layer of silver alloy, for example, a layer of silver coatedon one or both sides with a layer of indium cerium oxide (InCeO). SeeU.S. Pat. No. 5,667,853, incorporated herein in by reference.

The second conductive layer may be patterned irradiating themultilayered conductor/substrate structure with ultraviolet radiation sothat portions of the conductive layer are ablated therefrom. It is alsoknown to employ an infra-red (IR) fiber laser for patterning a metallicconductive layer overlying a plastic film, directly ablating theconductive layer by scanning a pattern over the conductor/filmstructure. See: Int. Publ. No. WO 99/36261 and “42.2: A New ConductorStructure for Plastic LCD Applications Utilizing ‘All Dry’ Digital LaserPatterning,” 1998 SID International Symposium Digest of TechnicalPapers, Anaheim, Calif., May 17–22, 1998, no. VOL. 29, May 17, 1998,pages 1099–1101, both incorporated herein by reference.

The LCD may also comprises at least one “functional layer” between theconductive layer and the substrate. The functional layer may comprise aprotective layer or a barrier layer. The protective layer useful in thepractice of the invention can be applied in any of a number of wellknown techniques, such as dip coating, rod coating, blade coating, airknife coating, gravure coating and reverse roll coating, extrusioncoating, slide coating, curtain coating, and the like. The lubricantparticles and the binder are preferably mixed together in a liquidmedium to form a coating composition. The liquid medium may be a mediumsuch as water or other aqueous solutions in which the hydrophiliccolloid are dispersed with or without the presence of surfactants. Apreferred barrier layer may acts as a gas barrier or a moisture barrierand may comprise SiOx, AlOx or ITO. The protective layer, for example,an acrylic hard coat, functions to prevent laser light from penetratingto functional layers between the protective layer and the substrate,thereby protecting both the barrier layer and the substrate. Thefunctional layer may also serve as an adhesion promoter of theconductive layer to the substrate.

In another embodiment, the polymeric support may further comprise anantistatic layer to manage unwanted charge build up on the sheet or webduring roll conveyance or sheet finishing. In the preferred embodiment,the display contains a functional antistatic layer which comprises aconductive material having areas of patterned coverage according to thepresent invention.

In another embodiment of this invention, the antistatic layer has asurface resistivity of between 10⁵ to 10¹². Above 10¹², the antistaticlayer typically does not provide sufficient conduction of charge tominimize charge accumulation to the point of preventing fog inphotographic systems or from unwanted point switching in liquid crystaldisplays. While layers greater than 10⁵ will minimize charge buildup,most antistatic materials are inherently not that conductive and inthose materials that are more conductive than 10⁵, there is usually somecolor associated with them that will reduce the overall transmissionproperties of the display. The antistatic layer is separate from thehighly conductive layer of ITO and provides the best static control whenit is on the opposite side of the web substrate from that of the ITOlayer. This may include the web substrate itself.

Another type of functional layer may be a color contrast layer. Colorcontrast layers may be radiation reflective layers or radiationabsorbing layers. In some cases, the rearmost substrate of each displaymay preferably be painted black. The color contrast layer may also beother colors. In another embodiment, the dark layer comprises millednonconductive pigments. The materials are milled below 1 micron to form“nano-pigments”. In a preferred embodiment, the dark layer absorbs allwavelengths of light across the visible light spectrum, that is from 400nanometers to 700 nanometers wavelength. The dark layer may also containa set or multiple pigment dispersions. Suitable pigments used in thecolor contrast layer may be any colored materials, which are practicallyinsoluble in the medium in which they are incorporated. Suitablepigments include those described in Industrial Organic Pigments:Production, Properties, Applications by W. Herbst and K. Hunger, 1993,Wiley Publishers. These include, but are not limited to, Azo Pigmentssuch as monoazo yellow and orange, diazo, naphthol, naphthol reds, azolakes, benzimidazolone, diazo condensation, metal complex, isoindolinoneand isoindolinic, polycyclic pigments such as phthalocyanine,quinacridone, perylene, perinone, diketopyrrolo-pyrrole, and thioindigo,and anthriquinone pigments such as anthrapyrimidine.

The functional layer may also comprise a dielectric material. Adielectric layer, for purposes of the present invention, is a layer thatis not conductive or blocks the flow of electricity. This dielectricmaterial may include a UV curable, thermoplastic, screen printablematerial, such as Electrodag 25208 dielectric coating from AchesonCorporation. The dielectric material forms a dielectric layer. Thislayer may include openings to define image areas, which are coincidentwith the openings. Since the image is viewed through a transparentsubstrate, the indicia are mirror imaged. The dielectric material mayform an adhesive layer to subsequently bond a second electrode to thelight modulating layer.

As used herein, the phrase “photographic element” is a material thatutilizes photosensitive silver halide in the formation of images. Thephotographic elements may be black and white, single color elements ormulticolor elements. Multicolor elements contain image dye-forming unitssensitive to each of the three primary regions of the spectrum. Eachunit may comprise a single emulsion layer or multiple emulsion layerssensitive to a given region of the spectrum. The layers of the element,including the layers of the image-forming units, may be arranged invarious orders as known in the art. In an alternative format, theemulsions sensitive to each of the three primary regions of the spectrummay be disposed as a single segmented layer.

For a display material used with this invention, at least one imagelayer containing silver halide and a dye forming coupler located on thetop side or surface and bottom side or surface of the imaging element issuitable. Applying the imaging layer to either the top and bottom issuitable for a photographic display material, but it is not sufficientto create a photographic display material that is optimum for both areflection display and a transmission display. For the display materialused with this invention, at least one image layer comprises at leastone dye forming coupler located on both the top and bottom of theimaging support used with this invention is preferred. Applying animaging layer to both the top and bottom of the support allows for thedisplay material to have the required density for both reflectiveviewing and for transmission viewing of the image. This duplitized“day/night” photographic display material has significant commercialvalue in that the day/night display material may be used for bothreflective viewing and transmission viewing. Prior art display materialswere optimized for either transmission viewing or reflective viewing butnot both simultaneously.

It has been found that the duplitized emulsion coverage should be in arange that is greater than 75% and less than 175% of typical emulsioncoverages for reflective consumer paper that contain typical amounts ofsilver and coupler. At coverages of less than 75% on the front side itwas found that a pleasing reflection print may not be obtained. Further,at coverages of less than 75% on the backside, pleasing transmissionimages may not be obtained. Coverages greater than 175% are undesirablebecause of the increased material expense and also because of the needfor extended development times in the processing solutions. In a morepreferred embodiment, emulsion laydowns should be from 100 to 150% ofthat found for a typical reflective consumer color paper.

The display material used with this invention wherein the amount of dyeforming coupler is substantially the same on the top and bottom sides ismost preferred because it allows for optimization of image density,while allowing for developer time less than 50 seconds. Further, coatingsubstantially the same amount of light sensitive silver halide emulsionon both sides has the additional benefit of balancing the imagingelement for image curl caused by the contraction and expansion of thehygroscopic gel typically found in photographic emulsions.

The photographic emulsions useful with this invention are generallyprepared by precipitating silver halide crystals in a colloidal matrixby methods conventional in the art. The colloid is typically ahydrophilic sheet forming agent such as gelatin, e, or derivativesthereof.

The crystals formed in the precipitation step are washed and thenchemically and spectrally sensitized by adding spectral sensitizing dyesand chemical sensitizers, and by providing a heating step during whichthe emulsion temperature is raised, typically from 40° C. to 70° C., andmaintained for a period of time. The precipitation and spectral andchemical sensitization methods utilized in preparing the emulsionsemployed with the invention may be those methods known in the art.

Chemical sensitization of the emulsion typically employs sensitizerssuch as: sulfur-containing compounds, for example, allyl isothiocyanate,sodium thiosulfate and allyl thiourea; reducing agents, for example,polyamines and stannous salts; noble metal compounds, for example, gold,platinum; and polymeric agents, for example, polyalkylene oxides. Asdescribed, heat treatment is employed to complete chemicalsensitization. Spectral sensitization is effected with a combination ofdyes, which are designed for the wavelength range of interest within thevisible or infrared spectrum. It is known to add such dyes both beforeand after heat treatment.

The silver halide emulsions utilized with this invention may becomprised of any halide distribution. Thus, they may be comprised ofsilver chloride, silver bromide, silver bromochloride, silverchlorobromide, silver iodochloride, silver iodobromide, silverbromoiodochloride, silver chloroiodobromide, silver iodobromochloride,and silver iodochlorobromide emulsions. It is preferred, however, thatthe emulsions be predominantly silver chloride emulsions. Bypredominantly silver chloride, it is meant that the grains of theemulsion are greater than 50 mole percent silver chloride. Preferably,they are greater than 90 mole percent silver chloride; and optimallygreater than 95 mole percent silver chloride.

The silver halide emulsions may contain grains of any size andmorphology. Thus, the grains may take the form of cubes, octahedrons,cubo-octahedrons, or any of the other naturally occurring morphologiesof cubic lattice type silver halide grains. Further, the grains may beirregular such as spherical grains or tabular grains. Grains having atabular or cubic morphology are preferred.

The photographic elements useful with the invention may utilizeemulsions as described in The Theory of the Photographic Process, FourthEdition, T. H. James, Macmillan Publishing Company, Inc., 1977, pages151–152. Reduction sensitization has been known to improve thephotographic sensitivity of silver halide emulsions. While reductionsensitized silver halide emulsions generally exhibit good photographicspeed, they often suffer from undesirable fog and poor storagestability.

Reduction sensitization may be performed intentionally by addingreduction sensitizers, chemicals that reduce silver ions to formmetallic silver atoms, or by providing a reducing environment such ashigh pH (excess hydroxide ion) and/or low pAg (excess silver ion).During precipitation of a silver halide emulsion, unintentionalreduction sensitization may occur when, for example, silver nitrate oralkali solutions are added rapidly or with poor mixing to form emulsiongrains. Also, precipitation of silver halide emulsions in the presenceof ripeners (grain growth modifiers) such as thioethers, selenoethers,thioureas, or ammonia tends to facilitate reduction sensitization.

Examples of reduction sensitizers and environments which may be usedduring precipitation or spectral/chemical sensitization to reductionsensitize an emulsion include ascorbic acid derivatives; tin compounds;polyamine compounds; and thiourea dioxide-based compounds described inU.S. Pat. Nos. 2,487,850; 2,512,925; and British Patent 789,823.Specific examples of reduction sensitizers or conditions, such asdimethylamineborane, stannous chloride, hydrazine, high pH (pH 8–11) andlow pAg (pAg 1–7) ripening are discussed by S. Collier in PhotographicScience and Engineering, 23, p. 113 (1979). Examples of processes forpreparing intentionally reduction sensitized silver halide emulsions aredescribed in EP 0 348 934 A1 (Yamashita), EP 0 369 491 (Yamashita), EP 0371 388 (Ohashi), EP 0 396 424 A1 (Takada), EP 0 404 142 A1 (Yamada),and EP 0 435 355 A1 (Makino).

The photographic elements useful with this invention may use emulsionsdoped with Group VIII metals such as iridium, rhodium, osmium, and ironas described in Research Disclosure, September 1994, Item 36544, SectionI, published by Kenneth Mason Publications, Ltd., Dudley Annex, 12aNorth Street, Emsworth, Hampshire PO10 7DQ, ENGLAND. Additionally, ageneral summary of the use of iridium in the sensitization of silverhalide emulsions is contained in Carroll, “Iridium Sensitization: ALiterature Review,” Photographic Science and Engineering, Vol. 24, No.6, 1980. A method of manufacturing a silver halide emulsion bychemically sensitizing the emulsion in the presence of an iridium saltand a photographic spectral sensitizing dye is described in U.S. Pat.No. 4,693,965. In some cases, when such dopants are incorporated,emulsions show an increased fresh fog and a lower contrast sensitometriccurve when processed in the color reversal E-6 process as described inThe British Journal of Photography Annual, 1982, pages 201–203.

A typical multicolor photographic element useful with the inventioncomprises a laminated support bearing a cyan dye image-forming unitcomprising at least one red-sensitive silver halide emulsion layerhaving associated therewith at least one cyan dye-forming coupler; amagenta image-forming unit comprising at least one green-sensitivesilver halide emulsion layer having associated therewith at least onemagenta dye-forming coupler; and a yellow dye image-forming unitcomprising at least one blue-sensitive silver halide emulsion layerhaving associated therewith at least one yellow dye-forming coupler. Theelement may contain additional layers, such as filter layers,interlayers, overcoat layers, subbing layers. The support useful withthe invention may also be utilized for black and white photographicprint elements.

When the base material used with the invention with the integraldiffusion layer is coated with silver halide photographic element, it iscapable of excellent performance when exposed by either an electronicprinting method or a conventional optical printing method. An electronicprinting method comprises subjecting a radiation sensitive silver halideemulsion layer of a recording element to actinic radiation of at least10⁻⁴ ergs/cm² for up to 100μ seconds duration in a pixel-by-pixel modewherein the silver halide emulsion layer is comprised of silver halidegrains as described above. A conventional optical printing methodcomprises subjecting a radiation sensitive silver halide emulsion layerof a recording element to actinic radiation of at least 10⁻⁴ ergs/cm²for 10⁻³ to 300 seconds in an imagewise mode wherein the silver halideemulsion layer is comprised of silver halide grains as described above.A radiation-sensitive emulsion comprised of silver halide grains (a)containing greater than 50 mole percent chloride, based on silver, (b)having greater than 50 percent of their surface area provided by {100}crystal faces, and (c) having a central portion accounting for from 95to 99 percent of total silver and containing two dopants selected tosatisfy each of the following class requirements: (i) a hexacoordinationmetal complex which satisfies the formula[ML₆]^(N)  (I)wherein n is zero, −1, −2, −3, or −4; M is a filled frontier orbitalpolyvalent metal ion, other than iridium; and L₆ represents bridgingligands which may be independently selected, provided that least four ofthe ligands are anionic ligands, and at least one of the ligands is acyano ligand or a ligand more electronegative than a cyano ligand; and(ii) an iridium coordination complex containing a thiazole orsubstituted thiazole ligand may be used with the present invention.

The combination of dopants (i) and (ii) provides greater reduction inreciprocity law failure than may be achieved with either dopant alone.The combination of dopants (i) and (ii) achieves reductions inreciprocity law failure beyond the simple additive sum achieved whenemploying either dopant class by itself. The combination of dopants (i)and (ii) provides greater reduction in reciprocity law failure,particularly for high intensity and short duration exposures. Thecombination of dopants (i) and (ii) further achieves high intensityreciprocity with iridium at relatively low levels, and both high and lowintensity reciprocity improvements even while using conventionalgelatino-peptizer (for example, other than low methioninegelatino-peptizer).

Improved reciprocity performance may be obtained for silver halidegrains (a) containing greater than 50 mole percent chloride, based onsilver, and (b) having greater than 50 percent of their surface areaprovided by {100} crystal faces by employing a hexacoordination complexdopant of class (i) in combination with an iridium complex dopantcomprising a thiazole or substituted thiazole ligand. The reciprocityimprovement is obtained for silver halide grains employing conventionalgelatino-peptizer, unlike the contrast improvement described for thecombination of dopants set forth in U.S. Pat. Nos. 5,783,373 and5,783,378, which requires the use of low methionine gelatino-peptizersas discussed therein, and which states it is preferable to limit theconcentration of any gelatino-peptizer with a methionine level ofgreater than 30 micromoles per gram to a concentration of less than 1percent of the total peptizer employed. It is specifically contemplatedto use significant levels (that is, greater than 1 weight percent oftotal peptizer) of conventional gelatin (for example, gelatin having atleast 30 micromoles of methionine per gram) as a gelatino-peptizer forthe silver halide grains of the emulsions useful with the invention. Agelatino-peptizer is employed which comprises at least 50 weight percentof gelatin containing at least 30 micromoles of methionine per gram, asit is frequently desirable to limit the level of oxidized low methioninegelatin which may be used for cost and certain performance reasons.

It may be contemplated to employ a class (i) hexacoordination complexdopant satisfying the formula:[ML₆]^(n)  (I)wherein

n is zero, −1, −2, −3, or −4;

M is a filled frontier orbital polyvalent metal ion, other than iridium,preferably Fe⁺², Ru⁺², Os⁺², Co⁺³, Rh⁺³, Pd⁺⁴ or Pt⁺⁴, more preferablyan iron, ruthenium or osmium ion, and most preferably a ruthenium ion;

L₆ represents six bridging ligands, which may be independently selected,provided that least four of the ligands are anionic ligands and at leastone (preferably at least 3 and optimally at least 4) of the ligands is acyano ligand or a ligand more electronegative than a cyano ligand. Anyremaining ligands may be selected from among various other bridgingligands, including aquo ligands, halide ligands (specifically, fluoride,chloride, bromide and iodide), cyanate ligands, thiocyanate ligands,selenocyanate ligands, tellurocyanate ligands, and azide ligands.Hexacoordinated transition metal complexes of class (i) which includesix cyano ligands are specifically preferred.

Illustrations of specifically contemplated class (i) hexacoordinationcomplexes for inclusion in the high chloride grains are provided by Olmet al U.S. Pat. No. 5,503,970 and Daubendiek et al U.S. Pat. Nos.5,494,789 and 5,503,971, and Keevert et al U.S. Pat. No. 4,945,035, aswell as Murakami et al Japanese Patent Application Hei-2[1990]-249588,and Research Disclosure Item 36736. Useful neutral and anionic organicligands for class (ii) dopant hexacoordination complexes are disclosedby Olm et al U.S. Pat. No. 5,360,712 and Kuromoto et al U.S. Pat. No.5,462,849.

Class (i) dopant is preferably introduced into the high chloride grainsafter at least 50 (most preferably 75 and optimally 80) percent of thesilver has been precipitated, but before precipitation of the centralportion of the grains has been completed. Preferably class (i) dopant isintroduced before 98 (most preferably 95 and optimally 90) percent ofthe silver has been precipitated. Stated in terms of the fullyprecipitated grain structure, class (i) dopant is preferably present inan interior shell region that surrounds at least 50 (most preferably 75and optimally 80) percent of the silver and, with the more centrallylocated silver, accounts the entire central portion (99 percent of thesilver), most preferably accounts for 95 percent, and optimally accountsfor 90 percent of the silver halide forming the high chloride grains.The class (i) dopant may be distributed throughout the interior shellregion delimited above or may be added as one or more bands within theinterior shell region.

Class (i) dopant may be employed in any conventional usefulconcentration. A preferred concentration range is from 10⁻⁸ to 10⁻³ moleper silver mole, most preferably from 10⁻⁶ to 5×10⁻⁴ mole per silvermole.

The following are specific illustrations of class (i) dopants:

-   (i-1) [Fe(CN)₆]⁻⁴-   (i-2) [Ru(CN)₆]⁻⁴-   (i-3) [Os(CN)₆]⁻⁴-   (i-4) [Rh(CN)₆]⁻³-   (i-5) [Co(CN)₆]⁻³-   (i-6) [Fe(pyrazine)(CN)₅]⁻⁴-   (i-7) [RuCl(CN)₅]⁻⁴-   (i-8) [OsBr(CN)₅]⁻⁴-   (i-9) [RhF(CN)₅]⁻³-   (i-10) [In(NCS)₆]⁻³-   (i-11) [FeCO(CN)₅]⁻³-   (i-12) [RuF₂(CN)₄]⁻⁴-   (i-13) [OsCl₂(CN)₄]⁻⁴-   (i-14) [RhI₂(CN)₄]⁻³-   (i-15) [Ga(NCS)₆]⁻³-   (i-16) [Ru(CN)₅(OCN)]⁻⁴-   (i-17) [Ru(CN)₅(N₃)]⁻⁴-   (i-18) [Os(CN)₅(SCN)]⁻⁴-   (i-19) [Rh(CN)₅(SeCN)]⁻³-   (i-20) [Os(CN)Cl₅]⁻⁴-   (i-21) [Fe(CN)₃Cl₃]⁻³-   (i-22) [Ru(CO)₂(CN)₄]⁻¹

When the class (i) dopants have a net negative charge, it is appreciatedthat they are associated with a counter ion when added to the reactionvessel during precipitation. The counter ion is of little importance,since it is ionically dissociated from the dopant in solution and is notincorporated within the grain. Common counter ions known to be fullycompatible with silver chloride precipitation, such as ammonium andalkali metal ions, are contemplated. It is noted that the same commentsapply to class (ii) dopants, otherwise described below.

The class (ii) dopant is an iridium coordination complex containing atleast one thiazole or substituted thiazole ligand. Careful scientificinvestigations have revealed Group VIII hexahalo coordination complexesto create deep electron traps, as illustrated R. S. Eachus, R. E. Gravesand M. T. Olm J. Chem. Phys., Vol. 69, pp. 4580–7 (1978) and PhysicaStatus Solidi A, Vol. 57, 429–37 (1980) and R. S. Eachus and M. T. OlmAnnu. Rep. Prog. Chem. Sect. C. Phys. Chem., Vol. 83, 3, pp. 3–48(1986). The class (ii) dopants are believed to create such deep electrontraps. The thiazole ligands may be substituted with any photographicallyacceptable substituent which does not prevent incorporation of thedopant into the silver halide grain. Exemplary substituents includelower alkyl (for example, alkyl groups containing 1–4 carbon atoms), andspecifically methyl. A specific example of a substituted thiazole ligandwhich may be used is 5-methylthiazole. The class (ii) dopant preferablyis an iridium coordination complex having ligands each of which are moreelectropositive than a cyano ligand. In a specifically preferred formthe remaining non-thiazole or non-substituted-thiazole ligands of thecoordination complexes forming class (ii) dopants are halide ligands.

It is specifically contemplated to select class (ii) dopants from amongthe coordination complexes containing organic ligands disclosed by Olmet al U.S. Pat. No. 5,360,712; Olm et al U.S. Pat. No. 5,457,021; andKuromoto et al U.S. Pat. No. 5,462,849.

In a preferred form it is contemplated to employ as a class (ii) dopanta hexacoordination complex satisfying the formula:[IrL¹ ₆]^(n′)  (II)wherein

n′ is zero, −1, −2, −3, or −4; and

L¹ ₆ represents six bridging ligands which may be independentlyselected, provided that at least four of the ligands are anionicligands, each of the ligands is more electropositive than a cyanoligand, and at least one of the ligands comprises a thiazole orsubstituted thiazole ligand. In a specifically preferred form at leastfour of the ligands are halide ligands, such as chloride or bromideligands.

Class (ii) dopant is preferably introduced into the high chloride grainsafter at least 50 (most preferably 85 and optimally 90) percent of thesilver has been precipitated, but before precipitation of the centralportion of the grains has been completed. Preferably class (ii) dopantis introduced before 99 (most preferably 97 and optimally 95) percent ofthe silver has been precipitated. Stated in terms of the fullyprecipitated grain structure, class (ii) dopant is preferably present inan interior shell region that surrounds at least 50 (most preferably 85and optimally 90) percent of the silver and, with the more centrallylocated silver, accounts the entire central portion (99 percent of thesilver), most preferably accounts for 97 percent, and optimally accountsfor 95 percent of the silver halide forming the high chloride grains.The class (ii) dopant may be distributed throughout the interior shellregion delimited above or may be added as one or more bands within theinterior shell region.

Class (ii) dopant may be employed in any conventional usefulconcentration. A preferred concentration range is from 10⁻⁹ to 10⁻⁴ moleper silver mole. Iridium is most preferably employed in a concentrationrange of from 10⁻⁸ to 10⁻⁵ mole per silver mole.

Specific illustrations of class (ii) dopants are the following:

-   (ii-1) [IrCl₅(thiazole)]⁻²-   (ii-2) [IrCl₄(thiazole)₂]⁻¹-   (ii-3) [IrBr₅(thiazole)]⁻²-   (ii-4) [IrBr₄(thiazole)₂]⁻¹-   (ii-S) [IrCl₅(5-methylthiazole)]⁻²-   (ii-6) [IrCl₄(5-methylthiazole)₂]⁻¹-   (ii-7) [IrBr₅(5-methylthiazole)]⁻²-   (ii-8) [IrBr₄(5-methylthiazole)₂]⁻¹

A layer using a magenta dye forming coupler, a class (ii) dopant incombination with an OsCl₅(NO) dopant has been found to produce apreferred result.

Emulsions may be realized by modifying the precipitation of conventionalhigh chloride silver halide grains having predominantly (>50%) {100}crystal faces by employing a combination of class (i) and (ii) dopantsas described above.

The silver halide grains precipitated contain greater than 50 molepercent chloride, based on silver. Preferably the grains contain atleast 70 mole percent chloride and, optimally at least 90 mole percentchloride, based on silver. Iodide may be present in the grains up to itssolubility limit, which is in silver iodochloride grains, under typicalconditions of precipitation, 11 mole percent, based on silver. It ispreferred for most photographic applications to limit iodide to lessthan 5 mole percent iodide, most preferably less than 2 mole percentiodide, based on silver.

Silver bromide and silver chloride are miscible in all proportions.Hence, any portion, up to 50 mole percent, of the total halide notaccounted for chloride and iodide, may be bromide. For color reflectionprint (that is, color paper) uses bromide is typically limited to lessthan 10 mole percent based on silver, and iodide is limited to less than1 mole percent based on silver.

In a widely used form high chloride grains are precipitated to formcubic grains—that is, grains having {100} major faces and edges of equallength. In practice ripening effects usually round the edges and cornersof the grains to some extent. However, except under extreme ripeningconditions substantially more than 50 percent of total grain surfacearea is accounted for by {100} crystal faces.

High chloride tetradecahedral grains are a common variant of cubicgrains. These grains contain 6 {100} crystal faces and 8 {111} crystalfaces. Tetradecahedral grains are within contemplation, to the extentthat greater than 50 percent of total surface area is accounted for by{100} crystal faces.

Although it is common practice to avoid or minimize the incorporation ofiodide into high chloride grains employed in color paper, it is has beenrecently observed that silver iodochloride grains with {100} crystalfaces and, in some instances, one or more {111} faces offer exceptionallevels of photographic speed. In the these emulsions iodide isincorporated in overall concentrations of from 0.05 to 3.0 mole percent,based on silver, with the grains having a surface shell of greater than50 Å that is substantially free of iodide and a interior shell having amaximum iodide concentration that surrounds a core accounting for atleast 50 percent of total silver. Such grain structures are illustratedby Chen et al EPO 0718679.

In another improved form the high chloride grains may take the form oftabular grains having {100} major faces. Preferred high chloride {100}tabular grain emulsions are those in which the tabular grains accountfor at least 70 (most preferably at least 90) percent of total grainprojected area. Preferred high chloride {100} tabular grain emulsionshave average aspect ratios of at least 5 (most preferably at least>8).Tabular grains typically have thicknesses of less than 0.3 μm,preferably less than 0.2 μm, and optimally less than 0.07 μm. Highchloride {100} tabular grain emulsions and their preparation aredisclosed by Maskasky U.S. Pat. Nos. 5,264,337 and 5,292,632; House etal U.S. Pat. No. 5,320,938; Brust et al U.S. Pat. No. 5,314,798; andChang et al U.S. Pat. No. 5,413,904.

Once high chloride grains having predominantly {100} crystal faces havebeen precipitated with a combination of class (i) and class (ii) dopantsdescribed above, chemical and spectral sensitization, followed by theaddition of conventional addenda to adapt the emulsion for the imagingapplication of choice may take any convenient conventional form. Theseconventional features are illustrated by Research Disclosure, Item38957, cited above, particularly:

-   III. Emulsion washing;-   IV. Chemical sensitization;-   V. Spectral sensitization and desensitization;-   VII. Antifoggants and stabilizers;-   VIII. Absorbing and scattering materials;-   IX. Coating and physical property modifying addenda; and-   X. Dye image formers and modifiers.

Some additional silver halide, typically less than 1 percent, based ontotal silver, may be introduced to facilitate chemical sensitization. Itis also recognized that silver halide may be epitaxially deposited atselected sites on a host grain to increase its sensitivity. For example,high chloride {100} tabular grains with corner epitaxy are illustratedby Maskasky U.S. Pat. No. 5,275,930. For the purpose of providing aclear demarcation, the term “silver halide grain” is herein employed toinclude the silver used to form the grain up to the point that the final{100} crystal faces of the grain are formed. Silver halide laterdeposited that does not overlie the {100} crystal faces previouslyformed accounting for at least 50 percent of the grain surface area isexcluded in determining total silver forming the silver halide grains.Thus, the silver forming selected site epitaxy is not part of the silverhalide grains while silver halide that deposits and provides the final{100} crystal faces of the grains is included in the total silverforming the grains, even when it differs significantly in compositionfrom the previously precipitated silver halide.

Image dye-forming couplers may be included in the element such ascouplers that form cyan dyes upon reaction with oxidized colordeveloping agents which are described in such representative patents andpublications as: U.S. Pat. Nos. 2,367,531; 2,423,730; 2,474,293;2,772,162; 2,895,826; 3,002,836; 3,034,892; 3,041,236; 4,883,746 and“Farbkuppler—Eine Literature Ubersicht,” published in Agfa Mitteilungen,Band III, pp. 156–175 (1961). Preferably such couplers are phenols andnaphthols that form cyan dyes on reaction with oxidized color developingagent. Also preferable are the cyan couplers described in, for instance,European Patent Application Nos. 491,197; 544,322; 556,700; 556,777;565,096; 570,006; and 574,948.

Typical cyan couplers are represented by the following formulas:

wherein R₁, R₅ and R₈ each represents a hydrogen or a substituent; R₂represents a substituent; R₃, R₄ and R₇ each represents an electronattractive group having a Hammett's substituent constant σ_(para) of 0.2or more and the sum of the σ_(para) values of R₃ and R₄ is 0.65 or more;R₆ represents an electron attractive group having a Hammett'ssubstituent constant σ_(para) of 0.35 or more; X represents a hydrogenor a coupling-off group; Z₁ represents nonmetallic atoms necessary forforming a nitrogen-containing, six-membered, heterocyclic ring which hasat least one dissociative group; Z₂ represents —C(R₇)═ —N═; and Z₃ andZ₄ each represents —C(R₈)═ and —N═.

Even more preferable are cyan couplers of the following formulas:

wherein R₉ represents a substituent (preferably a carbamoyl, ureido, orcarbonamido group); R₁₀ represents a substituent (preferablyindividually selected from halogens, alkyl, and carbonamido groups); R₁₁represents ballast substituent; R₁₂ represents a hydrogen or asubstituent (preferably a carbonamido or sulphonamido group); Xrepresents a hydrogen or a coupling-off group; and m is from 1–3.

A dissociative group has an acidic proton, for example, —NH—, —CH(R)—,that preferably has a pKa value of from 3 to 12 in water. Hammett's ruleis an empirical rule proposed by L. P. Hammett in 1935 for the purposeof quantitatively discussing the influence of substituents on reactionsor equilibria of a benzene derivative having the substituent thereon.This rule has become widely accepted. The values for Hammett'ssubstituent constants may be found or measured as is described in theliterature. For example, see C. Hansch and A. J. Leo, J. Med. Chem., 16,1207 (1973); J. Med. Chem., 20, 304 (1977); and J. A. Dean, Lange'sHandbook of Chemistry, 12th Ed. (1979) (McGraw-Hill).

Another type of preferred cyan coupler is an “NB coupler” which is adye-forming coupler which is capable of coupling with the developer4-amino-3-methyl-N-ethyl-N-(2-methanesulfonamidoethyl) anilinesesquisulfate hydrate to form a dye for which the left bandwidth (LBW)of its absorption spectra upon “spin coating” of a 3% w/v solution ofthe dye in di-n-butyl sebacate solvent is at least 5 nm less than theLBW for a 3% w/v solution of the same dye in acetonitrile. The LBW ofthe spectral curve for a dye is the distance between the left side ofthe spectral curve and the wavelength of maximum absorption measured ata density of half the maximum.

The “spin coating” sample is prepared by first preparing a solution ofthe dye in di-n-butyl sebacate solvent (3% w/v). If the dye isinsoluble, dissolution is achieved by the addition of some methylenechloride. The solution is filtered and 0.1–0.2 ml is applied to a clearpolyethylene terephthalate support (approximately 4 cm×4 cm) and spun at4,000 RPM using the Spin Coating equipment, Model No. EC101, availablefrom Headway Research Inc., Garland Tex. The transmission spectra of theso prepared dye samples are then recorded.

Preferred “NB couplers” form a dye which, in n-butyl sebacate, has a LBWof the absorption spectra upon “spin coating” which is at least 15 nm,preferably at least 25 nm, less than that of the same dye in a 3%solution (w/v) in acetonitrile.

A cyan dye-forming “NB coupler” which may be useful with the inventionhas the formula (IA)

wherein

R′ and R″ are substituents selected such that the coupler is a “NBcoupler”, as herein defined; and

Z is a hydrogen atom or a group which may be split off by the reactionof the coupler with an oxidized color developing agent.

The coupler of formula (IA) is a 2,5-diamido phenolic cyan couplerwherein the substituents R′ and R″ are preferably independently selectedfrom unsubstituted or substituted alkyl, aryl, amino, alkoxy andheterocyclyl groups.

The “NB coupler” has the formula (I):

wherein

R″ and R′″ are independently selected from unsubstituted or substitutedalkyl, aryl, amino, alkoxy and heterocyclyl groups and Z is ashereinbefore defined;

R₁ and R₂ are independently hydrogen or an unsubstituted or substitutedalkyl group; and

Typically, R″ is an alkyl, amino or aryl group, suitably a phenyl group.R′″ is desirably an alkyl or aryl group or a 5- to 10-memberedheterocyclic ring which contains one or more heteroatoms selected fromnitrogen, oxygen and sulfur, which ring group is unsubstituted orsubstituted.

In the preferred embodiment the coupler of formula (I) may be a2,5-diamido phenol in which the 5-amido moiety is an amide of acarboxylic acid which is substituted in the alpha position by aparticular sulfone (—SO₂—) group such as, for example, described in U.S.Pat. No. 5,686,235. The sulfone moiety is an unsubstituted orsubstituted alkylsulfone or a heterocyclyl sulfone or it is anarylsulfone, which is preferably substituted, in particular in the metaand/or para position.

Couplers having these structures of formulae (I) or (IA) comprise cyandye-forming “NB couplers” which form image dyes having verysharp-cutting dye hues on the short wavelength side of the absorptioncurves with absorption maxima (λ_(max)) which are shiftedhypsochromically and are generally in the range of 620–645 nm, which isideally suited for producing excellent color reproduction and high colorsaturation in color photographic papers.

Referring to formula (1), R₁ and R₂ are independently hydrogen or anunsubstituted or substituted alkyl group, preferably having from 1 to 24carbon atoms and, in particular, 1 to 10 carbon atoms, suitably amethyl, ethyl, n-propyl, isopropyl, butyl or decyl group or an alkylgroup substituted with one or more fluoro, chloro or bromo atoms, suchas a trifluoromethyl group. Suitably, at least one of R₁ and R₂ is ahydrogen atom, and if only one of R₁ and R₂ is a hydrogen atom, then theother is preferably an alkyl group having 1 to 4 carbon atoms, morepreferably 1 to 3 carbon atoms, and desirably two carbon atoms.

As used herein and throughout the specification unless wherespecifically stated otherwise, the term “alkyl” refers to an unsaturatedor saturated straight or branched chain alkyl group, including alkenyl,and includes aralkyl and cyclic alkyl groups, including cycloalkenyl,having 3–8 carbon atoms and the term ‘aryl’ includes specifically fusedaryl.

In formula (I), R″ is suitably an unsubstituted or substituted amino,alkyl or aryl group or a 5- to 10-membered heterocyclic ring whichcontains one or more heteroatoms selected from nitrogen, oxygen andsulfur, which ring is unsubstituted or substituted, but is more suitablyan unsubstituted or substituted phenyl group.

Examples of suitable substituent groups for this aryl or heterocyclicring include cyano, chloro, fluoro, bromo, iodo, alkyl- oraryl-carbonyl, alkyl- or aryl-oxycarbonyl, carbonamido, alkyl- oraryl-carbonamido, alkyl- or aryl-sulfonyl, alkyl- or aryl-sulfonyloxy,alkyl- or aryl-oxysulfonyl, alkyl- or aryl-sulfoxide, alkyl- oraryl-sulfamoyl, alkyl- or aryl-sulfonamido, aryl, alkyl, alkoxy,aryloxy, nitro, alkyl- or aryl-ureido and alkyl- or aryl-carbamoylgroups, any of which may be further substituted. Preferred groups arehalogen, cyano, alkoxycarbonyl, alkylsulfamoyl, alkyl-sulfonamido,alkylsulfonyl, carbamoyl, alkylcarbamoyl or alkylcarbonamido. Suitably,R″ is a 4-chlorophenyl, 3,4-di-chlorophenyl, 3,4-difluorophenyl,4-cyanophenyl, 3-chloro-4-cyanophenyl, pentafluorophenyl, or a 3- or4-sulfonamidophenyl group.

In formula (I) when R′″ is alkyl, it may be unsubstituted or substitutedwith a substituent such as halogen or alkoxy. When R′″ is aryl or aheterocycle, it may be substituted. Desirably, it is not substituted inthe position alpha to the sulfonyl group.

In formula (I), when R′″ is a phenyl group, it may be substituted in themeta and/or para positions with 1 to 3 substituents independentlyselected from the group consisting of halogen, and unsubstituted orsubstituted alkyl, alkoxy, aryloxy, acyloxy, acylamino, alkyl- oraryl-sulfonyloxy, alkyl- or aryl-sulfamoyl, alkyl- oraryl-sulfamoylamino, alkyl- or aryl-sulfonamido, alkyl- or aryl-ureido,alkyl- or aryl-oxycarbonyl, alkyl- or aryl-oxy-carbonylamino and alkyl-or aryl-carbamoyl groups.

In particular, each substituent may be an alkyl group such as methyl,t-butyl, heptyl, dodecyl, pentadecyl, octadecyl or1,1,2,2-tetramethylpropyl; an alkoxy group such as methoxy, t-butoxy,octyloxy, dodecyloxy, tetradecyloxy, hexadecyloxy or octadecyloxy; anaryloxy group such as phenoxy, 4-t-butylphenoxy or 4-dodecyl-phenoxy; analkyl- or aryl-acyloxy group such as acetoxy or dodecanoyloxy; an alkyl-or aryl-acylamino group such as acetamido, hexadecanamido or benzamido;an alkyl- or aryl-sulfonyloxy group such as methyl-sulfonyloxy,dodecylsulfonyloxy or 4-methylphenyl-sulfonyloxy; an alkyl- oraryl-sulfamoyl-group such as N-butylsulfamoyl orN-4-t-butylphenylsulfamoyl; an alkyl- or aryl-sulfamoylamino group suchas N-butyl-sulfamoylamino or N-4-t-butylphenylsulfamoyl-amino; an alkyl-or aryl-sulfonamido group such as methane-sulfonamido,hexadecanesulfonamido or 4-chlorophenyl-sulfonamido; an alkyl- oraryl-ureido group such as methylureido or phenylureido; an alkoxy- oraryloxy-carbonyl such as methoxycarbonyl or phenoxycarbonyl; an alkoxy-or aryloxy-carbonylamino group such as methoxy-carbonylamino orphenoxycarbonylamino; an alkyl- or aryl-carbamoyl group such asN-butylcarbamoyl or N-methyl-N-dodecylcarbamoyl; or a perfluoroalkylgroup such as trifluoromethyl or heptafluoropropyl.

Suitably, the above substituent groups have 1 to 30 carbon atoms, morepreferably 8 to 20 aliphatic carbon atoms. A desirable substituent is analkyl group of 12 to 18 aliphatic carbon atoms such as dodecyl,pentadecyl or octadecyl or an alkoxy group with 8 to 18 aliphatic carbonatoms such as dodecyloxy and hexadecyloxy or a halogen such as a meta orpara chloro group, carboxy or sulfonamido. Any such groups may containinterrupting heteroatoms such as oxygen to form for example polyalkyleneoxides.

In formula (I) or (IA), Z is a hydrogen atom or a group which may besplit off by the reaction of the coupler with an oxidized colordeveloping agent, known in the photographic art as a ‘coupling-offgroup’ and may preferably be hydrogen, chloro, fluoro, substitutedaryloxy or mercaptotetrazole, more preferably hydrogen or chloro.

The presence or absence of such groups determines the chemicalequivalency of the coupler, that is, whether it is a 2-equivalent or4-equivalent coupler, and its particular identity may modify thereactivity of the coupler. Such groups may advantageously affect thelayer in which the coupler is coated, or other layers in thephotographic recording material by performing, after release from thecoupler, functions such as dye formation, dye hue adjustment,development acceleration or inhibition, bleach acceleration orinhibition, electron transfer facilitation, color correction.

Representative classes of such coupling-off groups include, for example,halogen, alkoxy, aryloxy, heterocyclyloxy, sulfonyloxy, acyloxy, acyl,heterocyclylsulfonamido, heterocyclylthio, benzothiazolyl,phosophonyloxy, alkylthio, arylthio, and arylazo. These coupling-offgroups are described in the art, for example, in U.S. Pat. Nos.2,455,169; 3,227,551; 3,432,521; 3,467,563; 3,617,291; 3,880,661;4,052,212; and 4,134,766; and in U.K. Patent Nos. and publishedapplications 1,466,728; 1,531,927; 1,533,039; 2,066,755A, and2,017,704A. Halogen, alkoxy, and aryloxy groups are most suitable.

Examples of specific coupling-off groups are —Cl, —F, —Br, —SCN, —OCH₃,—OC₆H₅, —OCH₂C(═O)NHCH₂CH₂OH, —OCH₂C(O)NHCH₂CH₂OCH₃,—OCH₂C(O)NHCH₂CH₂OC(═O)OCH₃, —P(═O)(OC₂H₅)₂, —SCH₂CH₂COOH,

Typically, the coupling-off group is a chlorine atom, hydrogen atom, orp-methoxyphenoxy group.

It is essential that the substituent groups be selected so as toadequately ballast the coupler and the resulting dye in the organicsolvent in which the coupler is dispersed. The ballasting may beaccomplished by providing hydrophobic substituent groups in one or moreof the substituent groups. Generally a ballast group is an organicradical of such size and configuration as to confer on the couplermolecule sufficient bulk and aqueous insolubility as to render thecoupler substantially nondiffusible from the layer in which it is coatedin a photographic element. Thus, the combination of substituent aresuitably chosen to meet these criteria. To be effective, the ballastwill usually contain at least 8 carbon atoms and typically contains 10to 30 carbon atoms. Suitable ballasting may also be accomplished byproviding a plurality of groups which, in combination, meet thesecriteria. In the preferred embodiments useful with the invention, R₁ informula (I) is a small alkyl group or hydrogen. Therefore, in theseembodiments the ballast would be primarily located as part of the othergroups. Furthermore, even if the coupling-off group Z contains aballast, it is often desirable to ballast the other substituents aswell, since Z is eliminated from the molecule upon coupling; thus, theballast is most advantageously provided as part of groups other than Z.

The following examples further illustrate preferred cyan couplers to beused with the invention. It is not to be construed that the presentinvention is limited to these examples.

Preferred couplers are IC-3, IC-7, IC-35, and IC-36 because of theirsuitably narrow left bandwidths.

Couplers that form magenta dyes upon reaction with oxidized colordeveloping agent are described in such representative patents andpublications as: U.S. Pat. Nos. 2,311,082; 2,343,703; 2,369,489;2,600,788; 2,908,573; 3,062,653; 3,152,896; 3,519,429; 3,758,309; and“Farbkuppler-eine Literature Ubersicht,” published in Agfa Mitteilungen,Band III, pp. 126–156 (1961). Preferably such couplers are pyrazolones,pyrazolotriazoles, or pyrazolobenzimidazoles that form magenta dyes uponreaction with oxidized color developing agents. Especially preferredcouplers are 1H-pyrazolo [5,1-c]-1,2,4-triazole and 1H-pyrazolo[1,5-b]-1,2,4-triazole. Examples of 1H-pyrazolo [5,1-c]-1,2,4-triazolecouplers are described in U.K. Patent Nos. 1,247,493; 1,252,418;1,398,979; U.S. Pat. Nos. 4,443,536; 4,514,490; 4,540,654; 4,590,153;4,665,015; 4,822,730; 4,945,034; 5,017,465; and 5,023,170. Examples of1H-pyrazolo [1,5-b]-1,2,4-triazoles may be found in European Patentapplications 176,804; 177,765; U.S. Pat. Nos. 4,659,652; 5,066,575; and5,250,400.

Typical pyrazoloazole and pyrazolone couplers are represented by thefollowing formulas:

wherein R_(a) and R_(b) independently represent H or a substituent;R_(c) is a substituent (preferably an aryl group); R_(d) is asubstituent (preferably an anilino, carbonamido, ureido, carbamoyl,alkoxy, aryloxycarbonyl, alkoxycarbonyl, or N-heterocyclic group); X ishydrogen or a coupling-off group; and Z_(a), Z_(b), and Z_(c) areindependently a substituted methine group, ═N—, ═C—, or —NH—, providedthat one of either the Z_(a)-Z_(b) bond or the Z_(b)-Z_(c) bond is adouble bond and the other is a single bond, and when the Z_(b)-Z_(c)bond is a carbon-carbon double bond, it may form part of an aromaticring, and at least one of Z_(a), Z_(b), and Z_(c) represents a methinegroup connected to the group R_(b).

Specific examples of such couplers are:

Couplers that form yellow dyes upon reaction with oxidized colordeveloping agent are described in such representative patents andpublications as: U.S. Pat. Nos. 2,298,443; 2,407,210; 2,875,057;3,048,194; 3,265,506; 3,447,928; 3,960,570; 4,022,620; 4,443,536;4,910,126; and 5,340,703 and “Farbkuppler-eine Literature Ubersicht,”published in Agfa Mitteilungen, Band III, pp. 112–126 (1961). Suchcouplers are typically open chain ketomethylene compounds. Alsopreferred are yellow couplers such as described in, for example,European Patent Application Nos. 482,552; 510,535; 524,540; 543,367; andU.S. Pat. No. 5,238,803. For improved color reproduction, couplers whichgive yellow dyes that cut off sharply on the long wavelength side areparticularly preferred (for example, see U.S. Pat. No. 5,360,713).

Typical preferred yellow couplers are represented by the followingformulas:

wherein R₁, R₂, Q₁ and Q₂ each represents a substituent; X is hydrogenor a coupling-off group; Y represents an aryl group or a heterocyclicgroup; Q₃ represents an organic residue required to form anitrogen-containing heterocyclic group together with the >N—; and Q₄represents nonmetallic atoms necessary to from a 3- to 5-memberedhydrocarbon ring or a 3- to 5-membered heterocyclic ring which containsat least one hetero atom selected from N, O, S, and P in the ring.Particularly preferred is when Q₁ and Q₂ each represents an alkyl group,an aryl group, or a heterocyclic group, and R₂ represents an aryl ortertiary alkyl group.

Preferred yellow couplers may be of the following general structures:

Unless otherwise specifically stated, substituent groups which may besubstituted on molecules herein include any groups, whether substitutedor unsubstituted, which do not destroy properties necessary forphotographic utility. When the term “group” is applied to theidentification of a substituent containing a substitutable hydrogen, itis intended to encompass not only the substituent's unsubstituted form,but also its form further substituted with any group or groups as hereinmentioned. Suitably, the group may be halogen or may be bonded to theremainder of the molecule by an atom of carbon, silicon, oxygen,nitrogen, phosphorous, or sulfur. The substituent may be, for example,halogen, such as chlorine, bromine or fluorine; nitro; hydroxyl; cyano;carboxyl; or groups which may be further substituted, such as alkyl,including straight or branched chain alkyl, such as methyl,trifluoromethyl, ethyl, t-butyl, 3-(2,4-di-t-pentylphenoxy) propyl, andtetradecyl; alkenyl, such as ethylene, 2-butene; alkoxy, such asmethoxy, ethoxy, propoxy, butoxy, 2-methoxyethoxy, sec-butoxy, hexyloxy,2-ethylhexyloxy, tetradecyloxy, 2-(2,4-di-t-pentylphenoxy)ethoxy, and2-dodecyloxyethoxy; aryl such as phenyl, 4-t-butylphenyl,2,4,6-trimethylphenyl, naphthyl; aryloxy, such as phenoxy,2-methylphenoxy, alpha- or beta-naphthyloxy, and 4-tolyloxy;carbonamido, such as acetamido, benzamido, butyramido, tetradecanamido,alpha-(2,4-di-t-pentyl-phenoxy)acetamido,alpha-(2,4-di-t-pentylphenoxy)butyramido,alpha-(3-pentadecylphenoxy)-hexanamido,alpha-(4-hydroxy-3-t-butylphenoxy)-tetradecanamido,2-oxo-pyrrolidin-1-yl, 2-oxo-5-tetradecylpyrrolin-1-yl,N-methyltetradecanamido, N-succinimido, N-phthalimido,2,5-dioxo-1-oxazolidinyl, 3-dodecyl-2,5-dioxo-1-imidazolyl, andN-acetyl-N-dodecylamino, ethoxycarbonylamino, phenoxycarbonylamino,benzyloxycarbonylamino, hexadecyloxycarbonylamino,2,4-di-t-butylphenoxycarbonylamino, phenylcarbonylamino,2,5-(di-t-pentylphenyl)carbonylamino, p-dodecyl-phenylcarbonylamino,p-toluylcarbonylamino, N-methylureido, N,N-dimethylureido,N-methyl-N-dodecylureido, N-hexadecylureido, N,N-dioctadecylureido,N,N-dioctyl-N′-ethylureido, N-phenylureido, N,N-diphenylureido,N-phenyl-N-p-toluylureido, N-(m-hexadecylphenyl)ureido,N,N-(2,5-di-t-pentylphenyl)-N′-ethylureido, and t-butylcarbonamido;sulfonamido, such as methylsulfonamido, benzenesulfonamido,p-toluylsulfonamido, p-dodecylbenzenesulfonamido,N-methyltetradecylsulfonamido, N,N-dipropyl-sulfamoylamino, andhexadecylsulfonamido; sulfamoyl, such as N-methylsulfamoyl,N-ethylsulfamoyl, N,N-dipropylsulfamoyl, N-hexadecylsulfamoyl,N,N-dimethylsulfamoyl; N-[3-(dodecyloxy)propyl]sulfamoyl,N-[4-(2,4-di-t-pentylphenoxy)butyl]sulfamoyl,N-methyl-N-tetradecylsulfamoyl, and N-dodecylsulfamoyl; carbamoyl, suchas N-methylcarbamoyl, N,N-dibutylcarbamoyl, N-octadecylcarbamoyl,N-[4-(2,4-di-t-pentylphenoxy)butyl]carbamoyl,N-methyl-N-tetradecylcarbamoyl, and N,N-dioctylcarbamoyl; acyl, such asacetyl, (2,4-di-t-amylphenoxy)acetyl, phenoxycarbonyl,p-dodecyloxyphenoxycarbonyl, methoxycarbonyl, butoxycarbonyl,tetradecyloxycarbonyl, ethoxycarbonyl, benzyloxycarbonyl,3-pentadecyloxycarbonyl, and dodecyloxycarbonyl; sulfonyl, such asmethoxysulfonyl, octyloxysulfonyl, tetradecyloxysulfonyl,2-ethylhexyloxysulfonyl, phenoxysulfonyl,2,4-di-t-pentylphenoxysulfonyl, methylsulfonyl, octylsulfonyli,2-ethylhexylsulfonyl, dodecylsulfonyl, hexadecylsulfonyl,phenylsulfonyl, 4-nonylphenylsulfonyl, and p-toluylsulfonyl;sulfonyloxy, such as dodecylsulfonyloxy, and hexadecylsulfonyloxy;sulfinyl, such as methylsulfinyl, octylsulfinyl, 2-ethylhexylsulfinyl,dodecylsulfinyl, hexadecylsulfinyl, phenylsulfinyl,4-nonylphenylsulfinyl, and p-toluylsulfinyl; thio, such as ethylthio,octylthio, benzylthio, tetradecylthio,2-(2,4-di-t-pentylphenoxy)ethylthio, phenylthio,2-butoxy-5-t-octylphenylthio, and p-tolylthio; acyloxy, such asacetyloxy, benzoyloxy, octadecanoyloxy, p-dodecylamidobenzoyloxy,N-phenylcarbamoyloxy, N-ethylcarbamoyloxy, and cyclohexylcarbonyloxy;amino, such as phenylanilino, 2-chloroanilino, diethylamino,dodecylamino; imino, such as 1 (N-phenylimido)ethyl, N-succinimido or3-benzylhydantoinyl; phosphate, such as dimethylphosphate andethylbutylphosphate; phosphite, such as diethyl and dihexylphosphite; aheterocyclic group, a heterocyclic oxy group or a heterocyclic thiogroup, each of which may be substituted and which contain a 3- to7-membered heterocyclic ring composed of carbon atoms and at least onehetero atom selected from the group consisting of oxygen, nitrogen andsulfur, such as 2-furyl, 2-thienyl, 2-benzimidazolyloxy or2-benzothiazolyl; quaternary ammonium, such as triethylammonium; andsilyloxy, such as trimethylsilyloxy.

If desired, the substituents may themselves be further substituted oneor more times with the described substituent groups. The particularsubstituents used may be selected by those skilled in the art to attainthe desired photographic properties for a specific application and mayinclude, for example, hydrophobic groups, solubilizing groups, blockinggroups, releasing or releasable groups. Generally, the above groups andsubstituents thereof may include those having up to 48 carbon atoms,typically 1 to 36 carbon atoms and usually less than 24 carbon atoms,but greater numbers are possible depending on the particularsubstituents selected.

Representative substituents on ballast groups include alkyl, aryl,alkoxy, aryloxy, alkylthio, hydroxy, halogen, alkoxycarbonyl,aryloxcarbonyl, carboxy, acyl, acyloxy, amino, anilino, carbonamido,carbamoyl, alkylsulfonyl, arylsulfonyl, sulfonamido, and sulfamoylgroups wherein the substituents typically contain 1 to 42 carbon atoms.Such substituents may also be further substituted.

Stabilizers and scavengers that may be used with the present invention,but are not limited to, the following:

Examples of solvents which may be used in the invention include thefollowing:

Tritolyl phosphate S-1 Dibutyl phthalate S-2 Diundecyl phthalate S-3N,N-Diethyldodecanamide S-4 N,N-Dibutyldodecanamide S-5Tris(2-ethylhexyl)phosphate S-6 Acetyl tributyl citrate S-72,4-Di-tert-pentylphenol S-8 2-(2-Butoxyethoxy)ethyl acetate S-91,4-Cyclohexyldimethylene bis(2-ethylhexanoate) S-10

The dispersions used in photographic elements useful with the presentinvention may also include ultraviolet (UV) stabilizers and so-calledliquid UV stabilizers such as described in U.S. Pat. Nos. 4,992,358;4,975,360; and 4,587,346. Examples of UV stabilizers are shown below.

The aqueous phase may include surfactants. Surfactant may be cationic,anionic, zwitterionic or non-ionic. Useful surfactants include, but arenot limited to, the following:

Further, it is contemplated to stabilize photographic dispersions proneto particle growth through the use of hydrophobic, photographicallyinert compounds such as disclosed by Zengerle et al U.S. Pat. No.5,468,604.

In a preferred embodiment the invention may employ recording elementswhich are constructed to contain at least three silver halide emulsionand preferably six layer units. A suitable full color, multilayer formatfor a recording element used in the invention is represented byStructure I.

STRUCTURE I Red-sensitized cyan dye image-forming silver halide emulsionunit Interlayer Green-sensitized magenta dye image-forming silver halideemulsion unit Interlayer Blue-sensitized yellow dye image-forming silverhalide emulsion unit ///// Support ///// Blue-sensitized yellow dyeimage-forming silver halide emulsion unit Interlayer Green-sensitizedmagenta dye image-forming silver halide emulsion unit InterlayerRed-sensitized cyan dye image-forming silver halide emulsion unit

The image-forming units are separated from each other by hydrophiliccolloid interlayers containing an oxidized developing agent scavenger toprevent color contamination. Silver halide emulsions satisfying thegrain and gelatino-peptizer requirements described above may be presentin any one or combination of the emulsion layer units. Additional usefulmulticolor, multilayer formats for an element used with the inventioninclude structures as described in U.S. Pat. No. 5,783,373. Each of suchstructures in accordance with the invention preferably would contain sixsilver halide emulsions comprised of high chloride grains having atleast 50 percent of their surface area bounded by {100} crystal facesand containing dopants from classes (i) and (ii), as described above.Preferably each of the emulsion layer units contains emulsion satisfyingthese criteria.

Conventional features that may be incorporated into multilayer (andparticularly multicolor) recording elements contemplated for use in theinvention are illustrated by Research Disclosure, Item 38957, citedabove:

-   XI. Layers and layer arrangements-   XII. Features applicable only to color negative-   XIII. Features applicable only to color positive

B. Color reversal

C. Color positives derived from color negatives

-   XIV. Scan facilitating features.

The recording elements comprising the radiation sensitive high chlorideemulsion layers useful with this invention may be conventionallyoptically printed, or in accordance with a particular embodiment of theinvention may be image-wise exposed in a pixel-by-pixel mode usingsuitable high energy radiation sources typically employed in electronicprinting methods. Suitable actinic forms of energy encompass theultraviolet, visible, and infrared regions of the electromagneticspectrum, as well as electron-beam radiation and is convenientlysupplied by beams from one or more light emitting diodes or lasers,including gaseous or solid state lasers. Exposures may be monochromatic,orthochromatic, or panchromatic. For example, when the recording elementis a multilayer multicolor element, exposure may be provided by laser orlight emitting diode beams of appropriate spectral radiation, forexample, infrared, red, green or blue wavelengths, to which such elementis sensitive. Multicolor elements may be employed which produce cyan,magenta and yellow dyes as a function of exposure in separate portionsof the electromagnetic spectrum, including at least two portions of theinfrared region, as disclosed in the previously mentioned U.S. Pat. No.4,619,892. Suitable exposures include those up to 2000 nm, preferably upto 1500 nm. Suitable light emitting diodes and commercially availablelaser sources are known and commercially available. Imagewise exposuresat ambient, elevated, or reduced temperatures and/or pressures may beemployed within the useful response range of the recording elementdetermined by conventional sensitometric techniques, as illustrated byT. H. James, The Theory of the Photographic Process, 4th Ed., Macmillan,1977, Chapters 4, 6, 17, 18, and 23.

It has been observed that anionic [MX_(x)Y_(y)L_(z)] hexacoordinationcomplexes, where M is a group 8 or 9 metal (preferably iron, rutheniumor iridium), X is halide or pseudohalide (preferably Cl, Br, or CN) x is3 to 5, Y is H₂O, y is 0 or 1, L is a C—C, H—C or C—N—H organic ligand,and Z is 1 or 2, are surprisingly effective in reducing high intensityreciprocity failure (HIRF), low intensity reciprocity failure (LIRF) andthermal sensitivity variance and in an improving latent image keeping(LIK). As herein employed, HIRF is a measure of the variance ofphotographic properties for equal exposures, but with exposure timesranging from 10⁻¹ to 10⁻⁶ second. LIRF is a measure of the variance ofphotographic properties for equal exposures, but with exposure timesranging from 10⁻¹ to 100 seconds. Although these advantages may begenerally compatible with face centered cubic lattice grain structures,the most striking improvements have been observed in high (>50 mole %,preferably >90 mole %) chloride emulsions. Preferred C—C, H—C, or C—N—Horganic ligands are aromatic heterocycles of the type described in U.S.Pat. No. 5,462,849. The most effective C—C, H—C, or C—N—H organicligands are azoles and azines, either unsubstituted or containing alkyl,alkoxy, or halide substituents, where the alkyl moieties contain from 1to 8 carbon atoms. Particularly preferred azoles and azines includethiazoles, thiazolines, and pyrazines.

The quantity or level of high energy actinic radiation provided to therecording medium by the exposure source is generally at least 10⁻⁴ergs/cm², typically in the range of 10⁻⁴ ergs/cm² to 10⁻³ ergs/cm² andoften from 10⁻³ ergs/cm² to 10² ergs/cm². Exposure of the recordingelement in a pixel-by-pixel mode as known in the prior art persists foronly a very short duration or time. Typical maximum exposure times areup to 100μ seconds, often up to 10μ seconds, and frequently up to only0.5μ seconds. Single or multiple exposures of each pixel arecontemplated. The pixel density is subject to wide variation, as isobvious to those skilled in the art. The higher the pixel density, thesharper the images may be, but at the expense of equipment complexity.In general, pixel densities used in conventional electronic printingmethods of the type described herein do not exceed 10⁷ pixels/cm² andare typically in the range of 10⁴ to 10⁶ pixels/cm². An assessment ofthe technology of high-quality, continuous-tone, color electronicprinting using silver halide photographic paper which discusses variousfeatures and components of the system, including exposure source,exposure time, exposure level and pixel density and other recordingelement characteristics is provided in Firth et al., A Continuous-ToneLaser Color Printer, Journal of Imaging Technology, Vol. 14, No. 3, June1988. As previously indicated herein, a description of some of thedetails of conventional electronic printing methods comprising scanninga recording element with high energy beams such as light emitting diodesor laser beams, is set forth in Hioki U.S. Pat. No. 5,126,235 andEuropean Patent Applications 479 167 A1 and 502 508 A1.

Once imagewise exposed, the recording elements may be processed in anyconvenient conventional manner to obtain a viewable image. Suchprocessing is illustrated by Research Disclosure, Item 38957, citedabove:

XVIII. Chemical development systems

XIX. Development

XX. Desilvering, washing, rinsing, and stabilizing

In addition, a useful developer for the inventive material is ahomogeneous, single-part developing agent. The homogeneous, single-partcolor developing concentrate is prepared using a sequence of steps:

In the first step, an aqueous solution of a suitable color developingagent is prepared. This color developing agent is generally in the formof a sulfate salt. Other components of the solution may include anantioxidant for the color developing agent, a suitable number of alkalimetal ions (in an at least stoichiometric proportion to the sulfateions) provided by an alkali metal base, and a photographically inactivewater-miscible or water-soluble hydroxy-containing organic solvent. Thissolvent is present in the final concentrate at a concentration such thatthe weight ratio of water to the organic solvent is from 15:85 to 50:50.

In this environment, especially at high alkalinity, alkali metal ionsand sulfate ions form a sulfate salt that is precipitated in thepresence of the hydroxy-containing organic solvent. The precipitatedsulfate salt may then be readily removed using any suitable liquid/solidphase separation technique (including filtration, centrifugation, ordecantation). If the antioxidant is a liquid organic compound, twophases may be formed and the precipitate may be removed by discardingthe aqueous phase.

The color developing concentrates useful with this invention include oneor more color developing agents that are well known in the art that, inoxidized form, will react with dye forming color couplers in theprocessed materials. Such color developing agents include, but are notlimited to, aminophenols, p-phenylenediamines (especiallyN,N-dialkyl-p-phenylenediamines) and others which are well known in theart, such as EP 0 434 097 A1 (published Jun. 26, 1991) and EP 0 530 921A1 (published Mar. 10, 1993). It may be useful for the color developingagents to have one or more water-solubilizing groups as are known in theart. Further details of such materials are provided in ResearchDisclosure, 38957, pages 592–639 (September 1996). Research Disclosureis a publication of Kenneth Mason Publications Ltd., Dudley House, 12North Street, Emsworth, Hampshire PO10 7DQ England (also available fromEmsworth Design Inc., 121 West 19th Street, New York, N.Y. 10011). Thisreference will be referred to hereinafter as “Research Disclosure”.

Preferred color developing agents include, but are not limited to,N,N-diethyl p-phenylenediamine sulfate (KODAK Color Developing AgentCD-2), 4-amino-3-methyl-N-(2-methane sulfonamidoethyl)aniline sulfate,4-(N-ethyl-N-σ-hydroxyethylamino)-2-methylaniline sulfate (KODAK ColorDeveloping Agent CD-4), p-hydroxyethylethylaminoaniline sulfate,4-(N-ethyl-N-2-methanesulfonylaminoethyl)-2-methylphenylenediaminesesquisulfate (KODAK Color Developing Agent CD-3),4-(N-ethyl-N-2-methanesulfonylaminoethyl)-2-methylphenylenediaminesesquisulfate, and others readily apparent to one skilled in the art.

In order to protect the color developing agents from oxidation, one ormore antioxidants are generally included in the color developingcompositions. Either inorganic or organic antioxidants may be used. Manyclasses of useful antioxidants are known, including but not limited to,sulfites (such as sodium sulfite, potassium sulfite, sodium bisulfiteand potassium metabisulfite), hydroxylamine (and derivatives thereof),hydrazines, hydrazides, amino acids, ascorbic acid (and derivativesthereof), hydroxamic acids, aminoketones, mono- and polysaccharides,mono- and polyamines, quaternary ammonium salts, nitroxy radicals,alcohols, and oximes. Also useful as antioxidants are1,4-cyclohexadiones. Mixtures of compounds from the same or differentclasses of antioxidants may also be used if desired.

Especially useful antioxidants are hydroxylamine derivatives asdescribed, for example, in U.S. Pat. Nos. 4,892,804; 4,876,174;5,354,646; and 5,660,974, all noted above, and U.S. Pat. No. 5,646,327(Burns et al). Many of these antioxidants are mono- anddialkylhydroxylamines having one or more substituents on one or bothalkyl groups. Particularly useful alkyl substituents include sulfo,carboxy, amino, sulfonamido, carbonamido, hydroxy, and othersolubilizing substituents.

More preferably, the noted hydroxylamine derivatives may be mono- ordialkylhydroxylamines having one or more hydroxy substituents on the oneor more alkyl groups. Representative compounds of this type aredescribed, for example, in U.S. Pat. No. 5,709,982 (Marrese et al), ashaving the structure AI:

wherein R is hydrogen, a substituted or unsubstituted alkyl group of 1to 10 carbon atoms, a substituted or unsubstituted hydroxyalkyl group of1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group of5 to 10 carbon atoms, or a substituted or unsubstituted aryl grouphaving 6 to 10 carbon atoms in the aromatic nucleus.

X₁ is —CR₂(OH)CHR₁— and X₂ is —CHR₁CR₂(OH)— wherein R₁ and R₂ areindependently hydrogen, hydroxy, a substituted or unsubstituted alkylgroup or 1 or 2 carbon atoms, a substituted or unsubstitutedhydroxyalkyl group of 1 or 2 carbon atoms, or R₁ and R₂ togetherrepresent the carbon atoms necessary to complete a substituted orunsubstituted 5- to 8-membered saturated or unsaturated carbocyclic ringstructure.

Y is a substituted or unsubstituted alkylene group having at least 4carbon atoms, and has an even number of carbon atoms, or Y is asubstituted or unsubstituted divalent aliphatic group having an eventotal number of carbon and oxygen atoms in the chain, provided that thealiphatic group has a least 4 atoms in the chain.

Also in Structure AI, m, n, and p are independently 0 or 1. Preferably,each of m and n is 1, and p is 0. Specific di-substituted hydroxylamineantioxidants include, but are not limited to,N,N-bis(2,3-dihydroxypropyl)-hydroxylamine,N,N-bis(2-methyl-2,3-dihydroxypropyl)hydroxylamine, andN,N-bis(1-hydroxymethyl-2-hydroxy-3-phenylpropyl)hydroxylamine. Thefirst compound is preferred.

In the following Table, reference will be made to (1) ResearchDisclosure, December 1978, Item 17643, (2) Research Disclosure, December1989, Item 308119, and (3) Research Disclosure, September 1994, Item36544, all published by Kenneth Mason Publications, Ltd., Dudley Annex,12a North Street, Emsworth, Hampshire PO10 7DQ, ENGLAND. The Table andthe references cited in the Table are to be read as describingparticular components suitable for use with the invention. The Table andits cited references also describe suitable ways of preparing, exposing,processing and manipulating the elements, and the images containedtherein.

Reference Section Subject Matter 1 I, II Grain composition, morphology 2I, II, IX, X, XI, and preparation. Emulsion XII, XIV, XV preparationincluding hardeners, I, II, III, IX coating aids, addenda 3 A & B 1 III,IV Chemical sensitization and 2 III, IV spectral sensitization/ 3 IV, VDesensitization 1 V UV dyes, optical brighteners, 2 V luminescent dyes 3VI 1 VI Antifoggants and stabilizers 2 VI 3 VII 1 VIII Absorbing andscattering 2 VIII, XIII, XVI materials; Antistatic layers; 3 VIII, IX C& D matting agents 1 VII Image-couplers and image- 2 VII modifyingcouplers; Dye 3 X stabilizers and hue modifiers 1 XVII Supports 2 XVII 3XV 3 XI Specific layer arrangements 3 XII, XIII Negative workingemulsions; Direct positive emulsions 2 XVIII Exposure 3 XVI 1 XIX, XXChemical processing; 2 XIX, XX, XXII Developing agents 3 XVIII, XIX, XX3 XIV Scanning and digital processing procedures

The photographic elements may be exposed with various forms of energywhich encompass the ultraviolet, visible, and infrared regions of theelectromagnetic spectrum, as well as with electron beam, beta radiation,gamma radiation, x-ray, alpha particle, neutron radiation, and otherforms of corpuscular and wave-like radiant energy in either noncoherent(random phase) forms or coherent (in phase) forms, as produced bylasers. When the photographic elements are intended to be exposed byx-rays, they may include features found in conventional radiographicelement.

This allows for traditional image processing equipment to be used. Theimaging elements of this invention may be exposed via traditionaloptical methods using a negative, but they are preferably exposed bymeans of a collimated beam, to form a latent image, and then processedto form a visible image, preferably by other than heat treatment. Acollimated beam is preferred as it allows for digital printing andsimultaneous exposure of the imaging layer on the top and bottom sidewithout significant internal light scatter. A preferred example of acollimated beam is a laser also known as light amplification bystimulated emission of radiation. The laser may be preferred becausethis technology is used widely in a number of digital printing equipmenttypes. Further, the laser provides sufficient energy to simultaneouslyexpose the light sensitive silver halide coating on the top and bottomside of the display material without undesirable light scatter.Subsequent processing of the latent image into a visible image ispreferably carried out in the known RA-4™ (Eastman Kodak Company)process or other processing systems suitable for developing highchloride emulsions.

The present invention may also be used with an imaging assembly thatcomprises photohardenable microencapsulated coloring agents. Developmentis accomplished by the application of uniform pressure to the imagingassembly. Improved performance is obtained with respect to the imagingassembly's response to pressure by employing a support meeting certainbarrier properties. The imaging medium or assembly may also be referredto as a recording medium, and the imaging layer may be referred to as arecording layer, since the assembly may serve both to capture an image(either the original image or an electronic copy), as does film, andalso to display the image, as does a print. Consistent with this fact,the imaging assembly may form a positive image.

The photosensitive imaging layer (including microcapsules) is colored bypressure development after exposure to radiation based on imageinformation. The microcapsules, whose mechanical strength changes(increases) when exposed to light, are ruptured by means of pressuredevelopment, whereupon the coloring material and other substancesencapsulated in the microcapsules flow out (to varying amounts based onthe exposure) and development occurs. The coloring material, such as asubstantially colorless color former, migrates to, and reacts with, thedeveloper material and coloring occurs, whereupon a color image isdeveloped.

The “rupture” of the microcapsules are not an all-or-nothing event.Rather, the microcapsules exposed to light are differentially photocuredto release varying amounts of color former in order to achieve tonaldepth in the exposed area. The differential exposure to lightproportionately increases the viscosity of the photocurable compositionand thus immobilizes the color former proportionately to the desiredtonal depth in the exposed area. The rupture of the microcapsules andthe release of the color former are accomplished by the uniformapplication of pressure. Development of the photosensitive imaging layermay be accomplished, for example, by passing the imaging assemblybetween a pair of upper and lower nip rollers.

In the self-contained imaging system used with the present invention, animaging layer containing developer and photohardenable microcapsules maybe placed between two support members to form an integral unit, whereinat least one support is transparent and at least one support exhibits awater vapor transmission rate of less than 0.77 g/m 2/day (0.05 g/100 in2/day). Suitably, the transparent support has a percentage lighttransmission of at least 80 percent at a wavelength of 550 nm.Preferably, the barrier is also sealed on the sides to further preventwater vapor from permeating out of the imaging layer. The term “sealed,”as used herein, refers to a seal which is designed to be non-temporary.This seal is maintained during printing of the image and in the finalimaged product, as compared to a temporary package.

In the imaging assembly useful with the invention, a first support istransparent and a second support may be transparent or opaque. In thelatter case, an image is provided against a substantially whitebackground as viewed through the transparent support and, in the formercase, the image is viewed as a transparency preferably using an overheador slide projector. Sometimes herein the first support may be referredto as the “front” support and the second support may be referred to asthe “back” support.

The term “raw stock keeping” (RSK) is meant to describe the stability ofthe product from time of manufacture to time of use by the customer.Another metric of concern is “media shelf life” which is defined as thestability of the product from the time of opening a presealed packagecontaining the media to the time of consumption (printing) of the media.Typically, a package may contain a plurality of media, for example 20media.

As mentioned above, the self-contained imaging assembly comprises animaging layer or series of layers in which a color developing material(also referred to as a color developer) reacts with a dye precursor(also referred to as a color former) inside microcapsules. Typically,the microcapsules encapsulate photohardenable compositions comprising aphotosensitive initiator and hardenable material that undergoes a changeof mechanical strength when irradiated with light of a predeterminedwavelength, wherein the plurality of microcapsules encapsulates at leasta dye precursor for coloring when brought into contact with the colordeveloping material.

The plurality of microcapsules comprises three different types ofmicrocapsules. The three types of microcapsules encapsulate thepolymerization initiator, photocurable resin (each photocuring byirradiation with light of one of the three primary colors of light,respectively), and the colorless dye precursors for producing each ofthe colors of yellow, magenta and cyan. For example, when irradiatingthe self-contained imaging assembly with blue light (with a wavelengthof 470 nm), the photocurable resin of the microcapsules containing onlyyellow dye precursors is photocured, and these microcapsules (yellow)differentially rupture even when pressure developing the self-containedimaging assembly; however the microcapsules which were not photocured(magenta and cyan) rupture and the magenta and cyan dye precursors areforced out from the microcapsules and react with the color developingmaterial, whereupon coloring occurs, and these colors mix to become ablue color, whereupon this blue color may be seen through thelight-transmitting support.

Further, when irradiating the self-contained imaging assembly with greenlight (with a wavelength of 525 nm), the photocurable resin of themicrocapsules containing only magenta dye precursors is photocured, theyellow and cyan microcapsules are ruptured by pressure development, andas a result of the reaction of the color developing material with theyellow and cyan dye precursors the respective coloring occurs, whereuponthese colors mix to become a green color. Moreover, when irradiating theself-contained imaging assembly with red light (with a wavelength of 650nm), the photocurable resin of the microcapsules containing only cyandye precursors is photocured, the yellow and magenta microcapsules areruptured by pressure development, and as a result of the reaction of thecolor developing material with the yellow and magenta dye precursors therespective coloring occurs, whereupon these colors mix to become a redcolor.

Furthermore, when all microcapsules are photocured to maximum hardnessby exposure to light corresponding to the three types of microcapsulespreviously mentioned, they do not rupture even by pressure development.Therefore coloring does not occur, and the surface of the opaque supportmay be seen through the light-transmitting support, that is the surfacecolor (white in the present embodiment) of the opaque support becomesthe background color. In short, a color image is formed only in theareas where a coloring reaction occurred when the microcapsulesruptured. This coloring principal is sometimes called “self-coloring.”

The self-contained imaging assembly for use with the present inventionmay having a barrier layer in at least one, preferably both, of thesupports. The transparent support may be from 5 to 250 microns thick,preferably 10 to 125 microns thick, and has a light transmission of atleast 80% at a wavelength of 550 nm, preferably a light transmission ofat least 80% at a wavelength from 450 to 800 nm, more preferably a lighttransmission of at least 90% at 550 nm, most preferably from 450 to 800nm. In particular, at least one of the two supports, preferably both,have a water vapor transmission rate of less than 0.77 g/m 2/day (0.05g/100 in 2/day), preferably not more than 0.47 g/m 2/day (0.03 g/l 00 in2/day). The water vapor transmission rate is measured according to ASTMF-1249, hereby incorporated by reference. Although vapor transmissionrate is decreased by increasing thickness, increasing thickness maybegin to adversely affect the transparency of the support.

By the term “barrier layer” or “barrier material” is meant a materialthat has a water vapor transmission rate of less than 0.77 g/m ²/day(0.05 g/100 in 2/day) per 25 micron thickness of the material by theASTM F-1249 test. Since the barrier layer is part of a support, thesupport may have other layers that provide a higher water vaportransmission than the barrier layer, so long as the water vaportransmission rate of the entire “top” support, and preferably bothsupports, is less than 0.77 g/m²/day (0.05 g/100 in 2 day). The supportcomprising a barrier layer may be referred to as a “barrier support.” Aseparable part of the barrier support containing a barrier layer may bereferred to as a “barrier sheet,” for example, when referring to amaterial commercially available for use with the present invention.

Preferably, the top transparent support contains at least one layer thatis a barrier material. This barrier material may desirably have apreselected combination of properties, including thickness (if toothick, too hazy, if too thin not sufficient support) and opticalproperties. The barrier material may desirably be highly transparent,colorless, practical and cost effective, manufacturable or commerciallyavailable, able to be applied via coating or lamination, and stable(non-yellowing). This combination of properties is difficult to find ina single material. Many materials previously used in forming barriers inpackaging do not meet all the necessary criteria alone or at all, forexample, nylon, PC, PET, polyolefins, and saran polymers. The lattermaterials do not provide sufficient barrier properties unless usingthick layers that are impractical. Some materials, while having goodmoisture barrier properties, have an unacceptable tint, for examplesilicon oxide coated polyester films. Some materials with exceptionalmoisture barrier properties are not transparent, for example, aluminummetallized film or paper.

Thus, one embodiment for use with the present invention is directed to aself-contained photohardenable imaging assembly packaged for commercialsale wherein the assembly comprises, in order, a first transparentsupport that is 5 to 250 microns in thickness and has a lighttransmission of at least 80% at a wavelength of 550 nm and a water vaportransmission rate of less than 0.77 g/m²/day (0.05 g/l 00 in 2 day); oneor more imaging layers comprising a plurality of microcapsulesencapsulating a photohardenable composition and a color precursor whichmay react with a developing material in the same or an adjacent imaginglayer; and a second support which may be opaque or transparent that is 5to 250 microns thick.

In a preferred embodiment for use with the invention, the assembly issealed and the assembly is preconditioned to maintain said imaginglayers at a relative humidity greater within the range of from 40 to90%. The assembly may be sealed by means of heat or other means.

In yet another embodiment for use with the present invention, aself-contained photohardenable imaging assembly further comprises anintermediate layer comprising a relatively resilient material (comparedto first transparent support), wherein the Young's modulus of theresilient material is 0.02 to 10 ksi. This has been found beneficial forbetter distributing the pressure applied to the microcapsules duringdevelopment.

Materials which may be used as a barrier sheet for a transparent supportinclude, but are not limited to, fluorinated polymers, ceramic coatedpolymers, for example aluminum oxide, indium tin oxide, or siliconnitride coated on polyester or other transparent polymeric substrates,and other sheet materials meeting the above limitations. Especiallypreferred are Al₂O₃ vacuum deposited coatings on a polyester film (forexample, Toppan® GL-AE, available from Toppan Printing Co.) andchlorotrifluoroethylene homopolymer and copolymer films (for example,ACLAR® films available from Honeywell Corp.).

It is preferred that a barrier layer is on both sides of the imaginglayer in order to maintain the relative humidity within the assembly. Inone embodiment, the relative humidity within the assembly, andparticularly within the at least one imaging layer, is maintained atgreater than 40%, preferably greater than 50%, by sealing the front andback supports on the sides, after the imaging layer has equilibrated tothe desired relative humidity.

Adhesive materials useful for adhering the support to the emulsion orimaging layer may be selected from the general class of “modifiedacrylics” that have good adhesion, which may be formulated with improved“tack” by addition of tackifying resins or other chemical additives. Auseful adhesive may desirably be designed for high initial adhesion andfor adhesion to plastic substrates like polyester. It may desirably havethe ability to flow quickly for laminating to porous material (theimaging layer) and yet be inert with respect to the imaging layer. Highstrength adhesives useful in this invention, for example, are the filmlabel stock adhesives of the 3M Company; including 3M's #300 and #310adhesive formulas which exhibit “inertness” to the imaging layer. Otherexamples of adhesives useful in this invention are aqueous-basedadhesives such as Aeroset® 2177 or Aeroset® 2550, 3240, and 3250 whichare commercially available from Ashland Chemical Co., PD 0681, AP 6903,and W 3320 available from H. B. Fuller, or solvent-based pressuresensitive adhesives such as PS 508 sold by Ashland Chemical Co.

The adhesives may be used separately or in combination. Preferably, theadhesive is transparent or translucent and most preferably it is atransparent adhesive which remains transparent even after subjecting theassembly to actinic radiation and pressure necessary to image-wiseexpose and rupture the microcapsules. The amount of the adhesive willvary depending on the nature of the adhesive and the support. Theadhesive is generally applied in an amount of from 0.5 to 20 g/m².

A subbing layer for promoting adhesion between the transparent supportand the imaging layer may desirably have good compatibility with theimaging layer, may desirably not effect the sensitometric response ofthe imaging layer, and may desirably be chemically stable. Amorphouspolyesters, which may be applied as an aqueous dispersion, have beenfound to work well as the subbing layer material. Polymers withmolecular weights of 5,000–15,000, with a low hydroxyl number and lowacid number, may be employed, for example, the AQ polymers from EastmanChemical Co. and, more particularly, AQ38 and AQ55. The subbing layer iscoated onto the support at a dried coating weight of from 0.1 to 5.0 g/m2, with a preferred dried coating weight of from 0.5 to 2.0 g/m².

Preferably the subbing layer also includes an ultraviolet (UV) rayabsorber. Many types of UV absorbing materials have been described inthe prior art, including U.S. Pat. Nos. 3,215,530, 3,707,375, 3,705,805,3, 352,681, 3,278,448, 3,253,921, 3,738,837, 4,045,229, 4,790,959,4,853,471, 4,865,957, and 4,752,298, 5,977,219, 5,538,840 and UnitedKingdom Patent 1,338,265. Most preferred UV absorbers are polymeric UVabsorbers prepared by the method described in U.S. Pat. Nos. 4,496,650,4,431,726, 4,464,462 and 4,645,735, 5,620,838, EP 0 190 003, U.S. Pat.Nos. 3,761,272, 3,813,255, 4,431,726, 4,455,368, and 4,645,735.

Suitable photohardenable compositions, photoinitiators, chromogenicmaterials, carrier oils and encapsulation techniques for the layer ofmicrocapsules are disclosed in U.S. Pat. Nos. 4,440,846; 4,772,541; and5,230,982. Although the latter photohardenable compositions arenon-silver systems, silver-based photohardenable microencapsulatedsystem such as that described in U.S. Pat. Nos. 4,912,011; 5,091,280 and5,118,590 and other patents assigned to Fuji Photo Film Co are alsosuitable for use in the present invention.

In accordance with the preferred embodiments useful with the invention,a full color imaging system is provided in which the microcapsules aresensitive to red, green, and blue light, respectively. Thephotohardenable composition in at least one and preferably all threesets of microcapsules may be sensitized by a cationic dye-borate anioncomplex, e.g., a cyanine dye/borate complex as described in U.S. Pat.No. 4,772,541. For optimum color balance, the microcapsules aresensitive (lambda max) at 450 nm, 540 nm, and 650 nm, respectively. Sucha system is useful with visible light sources in direct transmission orreflection imaging. Such a material is useful in making contact printsor projected prints of color photographic slides. They are also usefulin electronic imaging using lasers, light emitting diodes, liquidcrystal displays or pencil light sources of appropriate wavelengths.

Because cationic dye-borate anion complexes absorb at wavelengthsgreater than 400 nm, they are colored. The unreacted dye complex presentin the microcapsules in the low density image areas may cause undesiredcoloration in the background area of the final picture, for example, themixture of microcapsules tends to be green which may give the lowdensity image areas a slight greenish tint. Approaches to reducingundesired coloration in the low density image area as well as thedeveloped image include reducing the amount of photoinitiator used,adjusting the relative amounts of cyan, magenta and yellowmicrocapsules, or providing a compensating tint in the white opaquesupport.

The photohardenable compositions used in the microcapsules may alsocontain a disulfide coinitiator. Examples of useful disulfides aredescribed in U.S. Pat. No. 5,230,982. By means of the optional use ofsuch disulfides, the amount of the photoinitiators used in themicrocapsules may be reduced to levels such that the backgroundcoloration or residual stain is less than 0.3 and preferably less than0.25 density units.

The photohardenable compositions useful with the present invention maybe encapsulated in various wall formers using conventional techniques,including coacervation, interfacial polymerization, polymerization ofone or more monomers in an oil, as well as various melting, dispersing,and cooling methods. To achieve maximum sensitivities, it is importantthat an encapsulation technique be used that provides high qualitycapsules which are responsive to changes in the internal phase viscosityin terms of their ability to rupture. Because the borate tends to beacid sensitive, encapsulation procedures conducted at higher pH (forexample, greater than 6) are preferred. Melamine-formaldehyde capsulesare particularly useful. U.S. Pat. No. 4,962,010 discloses aconventional encapsulation useful with the present invention in whichthe microcapsules are formed in the presence of pectin and sulfonatedpolystyrene as system modifiers. A capsule size may be selected whichminimizes light attenuation. The mean diameter of the capsules usedtypically ranges from approximately 1 to 25 microns. As a general rule,image resolution improves as the capsule size decreases. Technically,however, the capsules may range in size from one or more microns up tothe point where they become visible to the human eye.

The developer materials employed in carbonless paper technology areuseful. Illustrative examples are clay minerals such as acid clay,active clay, attapulgite, organic acids such as tannic acid, gallicacid, propyl gallate, acid polymers such as phenol-formaldehyde resins,phenol acetylene condensation resins, condensates between an organiccarboxylic acid having at least one hydroxy group and formaldehyde,metal salts of aromatic carboxylic acids or derivatives thereof such aszinc salicylate, tin salicylate, zinc 2-hydroxy naphthoate, zinc 3,5di-tert butyl salicylate, zinc 3,5-di-(a-methylbenzyl)salicylate, oilsoluble metals salts or phenol-formaldehyde novolak resins (for example,see U.S. Pat. Nos. 3,672,935 and 3,732,120) such as zinc modified oilsoluble phenol-formaldehyde resin as disclosed in U.S. Pat. No.3,732,120, zinc carbonate and mixtures thereof. The particle size of thedeveloper material may affect the quality of the image. In oneembodiment, the developer particles are selected to be in the range offrom 0.2 to 3 microns, preferably in the range of from 0.5 to 1.5microns. One or more suitable binders selected from polyethylene oxide,polyvinyl alcohol, polyacrylamide, acrylic latices, neoprene emulsions,polystyrene emulsions, and nitrile emulsions, may be mixed with thedeveloper and the microcapsules, typically in an amount of from 1 to 8%by weight, to prepare a coating composition. A preferred developermaterial is one which provides good compatibility with the microcapsuleslurry solution, for example Schenectady International resin HRJ-4250solution.

The self-contained imaging assembly used as photosensitive recordingmedium is not limited to the embodiments that have been describedbefore, but different variations or modifications thereof are possible.For example, instead of encapsulating the photocurable resin and thepolymerization initiator inside the microcapsules of the self-containedimaging assembly, the photocurable resin and the polymerizationinitiator may also be included in the material constituting themicrocapsules. Further, instead of photocurable microcapsules, theself-contained imaging assembly may contain photo-softeningmicrocapsules, for example, microcapsules which have sufficient strengthin the unexposed state, and which soften when exposed to light of apredetermined wavelength. In this case it is desirable to performthermal-curing by heat-fixing.

There is no need to use red, green and blue light to capture the imagein the imaging layer; depending on the characteristics of thephotosensitive recording medium, light with various wavelengths may beselected. For example, light emitting elements producing infrared light,red, and green, or light emitting elements producing far infrared light,near infrared light, and red may also be selected. Ultraviolet and farultraviolet are also advantageous examples of valid color choices forlight emitting elements. Moreover, the number of colors of the lightemitting elements is not limited to the three colors red, green, andblue; it is equally possible to use only one or two colors, or to selectfour colors, as in a typical color printer using yellow, magenta, cyan,and black, or even more colors. Furthermore, the choice of lightemitting elements includes, but is not limited to LEDs,electroluminescent lamps (EL), light emitting plasma and laser devices,and other light emitting elements.

The imaging assembly may be exposed in any suitable camera or otherexposure device to provide an image. The imaging assembly is especiallysuitable for exposure using a liquid crystal array or light emittingdiodes driven by a computer generated signal or a video signal for thereproduction of images from a video cassette recorder, or a camcorder.It is possible to utilize, for example, with the current state oftechnology, a very economical compact printer, weighing under 500 g andhaving a size less than 100,000 mm³ that prints directly from a digitalcamera utilizing a CompactFlash® card interface and provides aresolution of 150 ppi or more with continuous tone and over 250gradation levels.

The print is “developed,” based on the “latent image” formed by theselectively photohardened microencapsulated color formers, by theapplication of pressure or by the application of both heat and pressure.See, for example, the image forming device described in U.S. Pat. No.5,884,114 to Iwasaki, in which a photo and pressure sensitive printerprovides the feeding and discharging of a photosensitive imaging mediumat the front of the printer housing, which device may have the addedadvantage of being easily integrated into other equipment such as apersonal computer. In this particular device, the latent image is formedby a movement in the main scanning direction of an LED-type exposurehead. Thereafter, an upper nip roller of a developing mechanism is movedfrom a separated position to a pressing position. The capsules that havenot been photohardened are ruptured by pressure and a full color imageis formed on the sheet, heat-fixing (which is optional) is performed bya film heater, and the imaged assembly is discharged from the front ofthe housing for the device or printer.

A typical pressure-type image-forming device (which may be referred toas a printer) typically comprises a printer housing with a lightproofcartridge for accommodating photosensitive imaging media (alternatelyreferred to as recording media) mounted to the front of the printerhousing so as to be easily detachable. In some devices, a preheater isemployed for preheating the photosensitive imaging medium. A typicalexposure mechanism may include an exposure head for exposing whilescanning in a direction perpendicular to the surface of the drawing anda developing mechanism for pressure development by means of a pair of anupper and a lower nip roller. The roller may be maintained underpressure by a spring. An optional fixing heater for heat-fixing thedeveloped photosensitive imaging medium may be used. A discharge traymay be provided at the rear end of the printer housing. The pressuresensitive printer may be designed so that sheets are both fed anddischarged at the front side of the printer housing.

An image forming device for treatment of the imaging media can, forexample, comprise exposure means for forming a latent image on theimaging medium upon exposure based on image information, developingmeans for developing the latent image by means of the coloring materialcoming out of the microcapsules when pressure is applied to thephotosensitive imaging medium on which the latent image was formed bythe exposure means, wherein the developing means comprise a pair of anupper and a lower nip roller facing each other and sandwiching thetransport path of the photosensitive imaging medium, pressing means forpressing one nip roller against the other nip roller, roller switchingmeans for alternately switching between a pressing position in which theone nip roller is brought into pressure contact with the other niproller and a separated position in which the one nip roller is separatedfrom the other nip roller, and a transport path for transporting thephotosensitive imaging medium comprises a feed path for feeding thephotosensitive imaging medium on the inlet side, a discharge path fordischarging the recorded photosensitive imaging medium.

In one embodiment, the developing mechanism may comprise a pair of anupper and a lower nip roller, a rectangular frame fixed inside theprinter housing for supporting the nip rollers, a pair of compressionsprings for pressing both ends of the roller axis of the upper niproller toward the lower nip roller, and a roller switching mechanism foralternately switching between a pressing position in which the upper niproller is brought into pressure contact with the lower nip roller and aseparated position in which it is separated from the lower nip roller.If the pressing force of each of the springs is 150 kgf, the upper niproller presses with a total force of 300 kgf on the lower nip roller.However, other means for applying pressure may be employed, for example,a pressure stylus.

A control unit for the image-forming device may comprise a CPU, a ROMand a RAM, an I/O interface, and drive circuits, wherein a steppingmotor for paper transport, a solenoid actuator for driving a switchingplate, a film heater, a motor for roller switching, a stepping motor fordriving the carriage, the exposure head, are respectively connected tothe drive circuits. A connector and a control panel may also beconnected to the control unit. In one embodiment, image data (RGB imagedata) from an external host computer may be fed via a connector to thecontrol unit.

The ROM may store control programs for controlling all operations of theprinter, a control program for calculating, from the input image data,the duration for which each LED of the exposure head is turned on andthe timing thereof, a control program for controlling the transport ofthe self-contained imaging assembly by controlling the stepping motorfor sheet transport synchronously with the exposure to green, red andblue light, a control program for controlling the scanning of theexposure head by controlling the stepping motor for driving the carriagesynchronously with the exposure to green, red and blue light. Thedifferent buffers and memory types necessary for running the controlprograms are in the RAM. The number of copies to be printed, theenlargement or reduction ratio of the image, the size of the imageforming area of the imaging assembly, input by an operator at thecontrol panel, may be stored in the memory of the RAM. Exposure may takeplace upon calculation of the driving conditions for the stepping motor.

In one type of image-forming device, when image data of an image is sentto the control unit, the image data is divided into R image data, Gimage data, and B image data and stored in a buffer of the RAM. Each LEDof an exposure heat may be electrically driven by a drive circuit via acable.

Imaging medium sheets may be packaged as a stack of sheets which go intothe printer. The individual sheets may be picked from the stack ofsheets and transported into the “printing path” of the printer. However,if two or more sheets at the same time are picked up and fed into theprinting path the printer, the printer may become jammed, requiringdisassembly by the user. To avoid this problem, the static in the sheetsmay be reduced or eliminated just prior to the final packaging; and aprecision hinge on the printer film cassette or tray may be used. Also,a method to further aid the feeding of sheets into the printer is to adda “back coat” or backing layer to the imaging medium. In general, thesecoatings may include a binder and a grit or abrasive such as silica.Preferably, the front side of the first support and the back side of thesecond support has a coefficient of friction of less than 0.4.

The article or element of the invention may comprise a single layer ormultiple layers according to need. The antistatic layer may be placed inany location in the article or element, providing the layer is able toremain conductive. In one embodiment, the antistatic layer may be on thesame side of support as imaging layer. In another embodiment, theantistatic layer may be on the side of support opposite the imaginglayer. In other embodiments, the antistatic layer may be on top of theimaging layer (that is, one the side of the imaging layer opposite thesupport) or between the imaging layer and the support. There may also bemore than one antistatic layer. These multiple layers may be in anycombination of the above locations.

The multiplicity of other layers present in the article or element mayinclude any number of auxiliary layers such as backmark retentionlayers, tie layers or adhesion promoting layers, abrasion resistantlayers, conveyance layers, barrier layers, splice providing layers, UVabsorption layers, antihalation layers, optical effect providing layers,waterproofing layers, flavor retaining layers, fragrance providinglayers, adhesive layers, and imaging layers.

The article or element of the invention may be subjected to any numberof coatings and treatments, after extrusion, coextrusion, andorientation, or between casting and full orientation, to improve itsproperties, such as printability, barrier properties, heat-sealability,spliceability, adhesion to other supports and/or imaging layers.Examples of such coatings can be acrylic coatings for printability, andpolyvinylidene halide for heat seal properties. Examples of suchtreatments can be flame, plasma and corona discharge treatment, toimprove printability and adhesion. Further examples of treatments can becalendaring, embossing, and patterning to obtain specific effects on thesurface of the element. The element of the invention can be incorporatedin any other suitable support by lamination, extrusion coating, or anyother method known in the art.

The following examples are provided to illustrate the invention.

The photographic grade cellulose paper base used in the invention wasproduced using a standard fourdrinier paper machine and a blend ofmostly bleached hardwood Kraft fibers. The fiber ratio consistedprimarily of bleached poplar (38%) and maple/beech (37%) with lesseramounts of birch (18%) and softwood (7%). Fiber length was reduced from0.73 mm length weighted average as measured by a Kajaani FS-200 to 0.55mm length using high levels of conical refining and low levels of discrefining. Fiber lengths from the slurry were measured using a FS-200Fiber Length Analyzer (Kajaani Automation Inc.). Energy applied to thefibers as indicated by the total Specific Net Refining Power (SNRP) was127 KW hr/metric ton. Two conical refiners were used in series toprovide the total conical refiners SNRP value. This value was obtainedby adding the SNRPs of each conical refiner. Two disc refiners weresimilarly used in series to provide a total Disk SNRP. Neutral sizingchemical addenda, utilized on a dry weight basis, included alkyl ketenedimer at 0.20% addition, cationic starch (1.0%), polyaminoamideepichlorhydrin (0.50%), polyacrylamide resin (0.18%), diaminostilbeneoptical brightener (0.20%), and sodium bicarbonate. Surface sizing usinghydroxyethylated starch and sodium chloride was also employed but is notcritical to the invention. In the 3^(rd) Dryer section, ratio drying wasutilized to provide a moisture bias from the face side to the wire sideof the sheet. The imaging or face side (emulsion side) of the sheet wasthen remoisturized with conditioned steam immediately prior tocalendering. Sheet temperatures were raised to between 76° C. and 93° C.just prior to and during calendering. The paper was then calendered toan apparent density of 1.17 gm/cc. Moisture levels after the calenderwere 7.0% to 9.0% by weight.

EXAMPLE 1 Control

In this example a continuous antistatic layer was applied to a sheet ofphotographic polyethylene coated paper. The antistatic layer comprisedof the following ingredients:

Lithium nitrate  4.1% Carbowax ® (polyethylene glycol supplied by UnionCarbide)  3.6% Ludox ® AM (colloidal silica supplied by Du Pont) 18.5%Neocryl ® A50454 (styrene acrylate copolymer supplied by 73.8% Avecia)

The polyethylene coated paper represents a typical photographic paperbase of approximately 160 g/m² of photo quality paper with 26 g/m²pigmented of low density polyethylene (0.917 g/cc) on the top side. Thislayer contains approximately 12% by weight of anatase TiO₂, an opticalbrightener and blue tints. On the backside was a layer of 28 g/m² ofclear high density (0.924 g/cc) polyethylene. On the backsidepolyethylene resin a continuous antistatic layer was coated by a gravurecoating process.

In Examples 2 through 5, different dry coverages of the antistatic layercomprising the following ingredients were applied:

-   Baytron®P (a polythiophene based conductive polymer supplied by    Bayer) 5%-   Ludox® AM (colloidal silica supplied by Du Pont) 19%-   Neocryl® A50454 (styrene acrylate copolymer supplied by Avecia) 76%

EXAMPLE 2

In this example, polypropylene foam of caliper 6.0 mil and density 0.53g/cm³ was obtained from Berwick Industries, Berwick, Pa. This was thenextrusion resin coated on both sides using a flat sheet die. The upperflange or the face side of the foam was coextrusion coated. The layercloser to the foam was coated at 36 g/m² coverage, at a melt temperatureof 525° F., and comprised (approximately) 10% anatase TiO₂, 20% Mistron®CB Talc (from Luzenac America), 20% PA609 (amorphous organic polymerfrom Exxon Mobil) and 50% PF611 (polypropylene homopolymer—extrusioncoating grade from Basell). The layer furthest from the foam, referredto as the skin layer, was coated at 107 g/m² coverage, at a melttemperature of 300C, and comprised (approximately) 18% TiO₂, 4.5% ZnO,and 78.5% D4002 P (low density polyethylene from Eastman ChemicalCompany). The lower flange on the non-imaging or wire side of the foamwas monoextrusion coated at 300 C melt temperature. The lower flangecoating was at 485 g/m² coverage and comprised (approximately) 10%anatase TiO₂, 20% Mistron CB Talc, 20% PA609 and 50% PF611. The meltextruded polypropylene was extruded from a coathanger flat sheet die.The polymer was extruded into a nip formed by a chill roller and apressure roller with the polypropylene foam core sheet being the primaryweb substrate that was against the pressure roller and the moltenpolypropylene flange against the chill roller surface. The lower flange(non-imaging or backside flange) was then printed using an engravedgravure roller with the aforementioned polythiophene based antistaticlayer with a cross-hatch diagonal grid pattern. The grid lines formingthe conductive areas were approximately 1 mm wide and were spacedapproximately 3–5 mm apart, thus forming areas of non-antistatic coatedflange.

EXAMPLE 3

This example was the same as example 2, but instead of coating a gridpattern on the backside, a continuous antistatic layer was applied.

EXAMPLE 4

This example is the same as example 2, but was coated on a sheet of 4mil clear polyester.

EXAMPLE 5

This example was the same as example 2, except the base was coated twicewith the antistatic layer. The first coating was applied with acontinuous pattern gravure roller with a coverage of the antistaticlayer that yielded a surface resistivity of 10^12. The antistatic layerwas dried and then coated with the grid roller and another antistaticlayer as described in example 2. This was done to determine whetherthere was a need for a weak conductor to bleed charge into the primarygrid pattern.

Sample Evaluation

The samples were evaluated for surface electrical resistivity (SER) witha Keithly model 616 digital electrometer using a two point DC probe by amethod similar to that described in U.S. Pat. No. 2,801,191 (col. 4,lines 4–34). Additionally the samples were evaluated for visibility ofthe pattern of the antistatic layer.

TABLE 1 Surface Resistivity Appearance of Unwind static Example Ohms/Sq.Pattern* discharge** 1 (control A) 10{circumflex over( )}12–10{circumflex over ( )}13  Low low 2 10{circumflex over( )}9–10{circumflex over ( )}10 Low but slight low pattern noted in somelighting conditions. 3 (control B) 10{circumflex over( )}9–10{circumflex over ( )}10 Low low 4 10{circumflex over( )}9–10{circumflex over ( )}10 Low but slight low pattern noted in somelighting conditions. 5 10{circumflex over ( )}9–10{circumflex over( )}10 Low but slight low pattern noted in some lighting conditions.*The antistatic layer was visually judged on a low/med/high scale withlow being not visible to slightly, but not significantly, visible**Unwind static was observed by unwinding slit rolls of the variousbases at the same speed in a darken room.

As noted by the results in Table 1, the control sample showed littlevisibility of the continuous antistatic layer as compared to those witha pattern as represented by examples 2, 4 and 5 and also the continuousantistatic layer in example 3. All examples had good surface resistivityresults. Since the control (Example 1, Control A) of resin coated paperhas both moisture and an ionic salt within the paper base the overallconductivity required to minimize static discharge was less than theother examples. When comparing the surface resistivity results of thepatterned examples (2,4 and vs. control B (same antistatic layer but acontinuous coating), the overall resistivity and static discharge wereabout the same.

EXAMPLE 6 Invention

A liquid crystal display is prepared as follows: A 125 micronpolyethylene terephthalate support is coated with a layer of ITO (300ohm per square resistively) forming the first electrode one side of thesupport and a patterned transparent antistatic layer on the sideopposite the ITO layer. The patterned transparent antistatic layer isformed by coating an aqueous composition comprising a binder and aconductive agent with a weight ratio of 40:60, resulting in a layer withconductivity of 10.2 log ohms per square. Polyethyleneimine (such asMica A-131-X, supplied by the Mica Corporation) is used as the polymericbinder, and a cross-linked vinylbenzyl quaternary ammonium polymer isused as the conductive agent.

The ITO is laser etched with thin lines to electrically separate rows inthe first electrode. Each row corresponds to an individual character inthe display. An imageable layer containing gelatin and droplets ofcholesteric liquid crystal is coated on the ITO layer. A colorcontrasting black layer containing gelatin and cyan, magenta, yellow,and black pigments is coated on the imageable layer. Thin bands of thetwo coated layers are removed along on an edge of the displayperpendicular to the laser etch lines. This exposes the ITO along theedge of the display to allow electrical contact to the first electrode.

A conductive UV curable ink is then screen printed on the colorcontrasting layer and exposed to UV. The screen patterns the conductiveink to form segments of characters in a seven-segment display. Thesesegments form the second electrode. After curing is complete, thematerial is screen printed with a UV curable dielectric ink, and exposedto UV radiation. The screen patterns the dielectric to surround andcover the conductive segments leaving only a small via hole over eachsegment. The via-hole allows subsequent electrical contact. Thedielectric ink also covers the exposed ITO except for via holes thatallow subsequent electrical contact to the first electrode. After curingis complete the material is again screen printed with a second layer ofUV curable dielectric and exposed to UV radiation. The screen has thesame pattern as the first pass of dielectric ink. After curing iscomplete the material is screen printed with UV curable conductive ink,exposed to UV radiation. The screen patterns the conductive ink to formelectrical traces and contact pads. The contact pads are used to connectthe display to external drive electronics. The traces carry electricalsignals from the contact pads to the individual segments making contactto the second electrode through the via-holes in the dielectric layers.Pads also cover areas of exposed ITO through via-holes in the dielectriclayers to make contact with the first electrode.

EXAMPLE 7 Control

A liquid crystal display was prepared as in Example 6, except there wasno transparent patterned antistatic layer on the support.

Examples 6 and 7 are evaluated for unwind static by unwinding slit rollsof the various displays at the same speed in a darkened room. Thedisplays are evaluated for localized point switching by visualexamination. Example 6 of the invention will have fewer localized pointswitches than the control Example 7 without the transparent patternedantistatic layer of the invention.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

1. A display comprising a substrate having deposited on the surfacethereof an electrically modulated imaging layer, at least oneelectrically conductive layer having a surface conductivity of less than10⁴ ohms/sq, and at least one transparent antistatic layer, wherein saidantistatic layer comprises a conductive material having areas ofpatterned coverage which comprises a continuous conductive pathway andwherein said antistatic layer comprises a surface resistivity of between10⁵ and 10¹² ohms/sq.
 2. The display of claim 1 wherein said substrateis flexible.
 3. The display of claim 1 wherein said substrate istransparent.
 4. The display of claim 3 wherein said transparentsubstrate comprises polyester.
 5. The display of claim 3 wherein saidtransparent substrate comprises polycarbonate.
 6. The display of claim 3wherein said transparent substrate comprises polyethylene naphthalate(PEN).
 7. The display of claim 3 wherein said transparent substratecomprises acetate.
 8. The display of claim 3 wherein said transparentsubstrate comprises polyethersulfone.
 9. The display of claim 3 whereinsaid transparent substrate comprises at least one member selected fromthe group consisting of polyolefin, polyester, polycarbonate, acetate,cyclic polyolefin, polyethersulfone, and polyamide.
 10. The display ofclaim 1 wherein said electrically modulated imaging layer comprises alight modulating material.
 11. The display of claim 9 wherein said lightmodulating material comprises a liquid crystal material.
 12. The displayof claim 11 wherein said liquid crystal material is a cholesteric liquidcrystal material.
 13. The display of claim 1 wherein the imaging layercontains a polymer dispersed cholesteric liquid crystal layer.
 14. Thedisplay of claim 13 wherein said polymer is gelatin.
 15. The display ofclaim 13 wherein said polymer is water soluble.
 16. The display of claim1 wherein said electrically modulated imaging layer is capable offorming an image or text.
 17. The display of claim 1 wherein said atleast one conductive layer is patterned with actinic radiation.
 18. Thedisplay of claim 1 wherein said conductive layer comprises ITO.
 19. Thedisplay of claim 1 wherein said conductive material comprises at leastone polyether polymeric conductive material.
 20. The display of claim 19wherein said polyether polymeric conductive material comprises polyetherblock copolyamide.
 21. The display of claim 1 wherein said conductivematerial comprises a transparent conductive material.
 22. The display ofclaim 21 wherein said transparent conductive material comprises amaterial transparent to visible light in the range from 400 to 700 nm.23. The display of claim 1 wherein said conductive material comprises atleast one electronic conductor.
 24. The display of claim 23 wherein saidelectronic conductor comprises metal-containing particles.
 25. Thedisplay of claim 24 wherein said metal-containing particles areacicular.
 26. The display of claim 24 wherein said metal-containingparticles comprise semiconducting metal oxides.
 27. The display of claim24 wherein said metal-containing particles comprise conductivecrystalline inorganic oxides.
 28. The display of claim 27 wherein saidmetal-containing particles comprise tin oxide.
 29. The display of claim24 wherein said metal-containing particles comprise conductive metalantimonates.
 30. The display of claim 24 wherein said metal-containingparticles comprise conductive inorganic non-oxides.
 31. The display ofclaim 23 wherein said electronic conductor comprises electronicallyconductive polymers.
 32. The display of claim 31 wherein saidelectronically conductive polymers comprise polythiophenes,polypyrroles, and polyanilines.
 33. The display of claim 1 wherein saidconductive material comprises at least one ionic conductor.
 34. Thedisplay of claim 33 wherein said ionic conductor is an inorganic and/ororganic salt.
 35. The display of claim 33 wherein said ionic conductoris a conductive clay.
 36. The display of claim 33 wherein said ionicconductor is a surfactant capable of static dissipation.
 37. The displayof claim 36 wherein said surfactant is an alkyl sulfates, alkylsulfonates and alkyl phosphates having alkyl chains of 4 or more carbonatoms in length.
 38. The display of claim 36 wherein said surfactant isan onium salt, having alkyl chains of 4 or more carbon atoms in length.39. The display of claim 36 wherein said surfactant is polyvinylalcohol, polyvinylpyrrolidone, polyether, amine, acids and fatty acidesters having alkyl groups of 4 or more carbon atoms in length.
 40. Thearticle of claim 1 wherein said patterned coverage comprises areas ofcoverage and areas without coverage.
 41. The article of claim 40 whereinsaid patterned coverage comprises a shape.
 42. The article of claim 40wherein said areas of coverage comprise at least one line.
 43. Thearticle of claim 40 wherein said areas of coverage comprise at least onedot.
 44. The article of claim 1 wherein said patterned coveragecomprises a grid.
 45. The article of claim 1 wherein said patternedcoverage comprises a gradient, wherein said gradient comprises areas ofhigher coverage and lower coverage.
 46. The article of claim 45 whereinsaid areas of higher coverage comprise a resistivity of from 10⁵ to 10¹²ohm/sq and said areas of lower coverage comprise a resistivity ofgreater than 10¹² ohm/sq.
 47. The article of claim 1 wherein saidantistatic layer comprises a layer applied by blade coating, wound wirerod coating, slot coating, slide hopper coating, gravure, or curtaincoating.
 48. The article of claim 1 wherein said antistatic layercomprises a layer applied by extrusion coating.
 49. The article of claim48 wherein said extrusion coating comprises simultaneous or consecutiveextrusion.
 50. The article of claim 1 wherein said antistatic layercomprises a printed layer.
 51. The article of claim 1 wherein saidsupport comprises an opaque support.
 52. The article of claim 51 whereinsaid opaque support comprises paper.
 53. The article of claim 1 whereinsaid support comprises oriented laminates.
 54. The article of claim 1wherein said support comprises a transparent support.
 55. The article ofclaim 1 wherein said conductive material comprises from 15 to 85% weightof said antistatic layer, and said polymer comprises from 15 to 85% byweight of said antistatic layer.
 56. The article of claim 1 wherein saidantistatic layer further comprises a polymer.
 57. The article of claim56 wherein said polymer comprises polypropylene.
 58. The article ofclaim 56 wherein said polymer comprises polyethylene.
 59. The article ofclaim 56 wherein said polymer comprises polyurethane.
 60. The article ofclaim 56 wherein said polymer comprises polymers and interpolymersselected from the group of polymers and interpolymers prepared frommonomers selected from the group consisting of styrene, styrenederivatives, acrylic acid, acrylic acid derivatives, methacrylic acid,methacrylic acid derivatives, olefins, chlorinated olefins,acrylonitriles, methacrylonitriles, itaconic acid, itaconic acidderivatives, maleic acid, maleic acid derivatives, vinyl halides,vinylidene halides, vinyl monomer having a primary amine addition salt,and vinyl monomer containing an aminostyrene addition salt.
 61. Thearticle of claim 56 wherein said polymer comprises styrene and styrenederivates, acrylics and acrylic acid derivatives, methacrylic acid andmethacrylic acid derivatives.
 62. The article of claim 56 wherein saidpolymer comprises polyester.
 63. The article of claim 1 wherein saidantistatic layer comprises a layer on the same side of said support assaid imaging layer.
 64. The article of claim 1 wherein said antistaticlayer comprises a layer on the side of said support opposite saidimaging layer.
 65. The article of claim 1 wherein said antistatic layeris on the side of said imaging layer opposite said support.
 66. Thearticle of claim 1 wherein said antistatic layer is between said imaginglayer and said support.
 67. The display of claim 1 further comprising atleast a second electrically conductive layer.
 68. The display of claim 1wherein the imaging layer further comprises a radiation absorbing layer.69. A display comprising a substrate having deposited on the surfacethereof an electrically modulated imaging layer, at least oneelectrically conductive layer, and at least one transparent antistaticlayer, wherein said antistatic layer comprises a conductive materialhaving areas of patterned coverage, wherein said patterned coveragecomprises a gradient, wherein said gradient comprises areas of highercoverage comprising a resistivity of from 10⁵ to 10¹² ohm/sq and areasof lower coverage comprising a resistivity of greater than 10¹² ohm/sq.70. A display comprising a substrate having deposited on the surfacethereof an electrically modulated imaging layer, at least oneelectrically conductive layer having a surface conductivity of less than10⁴ ohms/sq, and at least one transparent antistatic layer, wherein saidantistatic layer comprises a conductive material having areas ofpatterned coverage which comprises a continuous conductive pathway andwherein said antistatic layer comprises a surface resistivity of between10⁵ and 10¹² ohms/sq., wherein said antistatic layer comprises a layeron the side of said support opposite said imaging layer.